Y 


EVENINGS  AT  THE  MICROSCOPE; 

OB, 

RESEARCHES 

AMONG  THE  MINUTER  ORGANS  AND  FORMS*  OF 

ANIMAL     LIEE. 

BY 

PHILIP    HENRY    GOSSE,    F.R.S. 

A    NEW    EDITION,    REVISED    AND    ANNOTATED. 


PUBLISHED   UNDER  THE   DIRECTION   OF   THB 

COMMITTEE     OP     GENERAL     LITERATURE     AND     EDUCATION, 

APPOINTED   BY  THB    SOCIETY    FOR  PROMOTING 

CHRISTIAN   KNOWLEDGE. 


LONDON : 

.SOCIETY  FOR  PROMOTING  CHRISTIAN  KNOWLEDGE; 
NORTHUMBERLAND  AVENUE,  CHARING  CROSS,  W.C.  ; 

43,  QUEEN  VICTORIA  STREET,  B.C. ; 
26,  ST.  GEORGE'S  PLACE,  HYDB  PARK  COBNBB,  8.W. 

BRIGHTON :    135,    NORTH   STREET. 
NEW  YORK  :   E.  &  J.   B.  YOUNG  &  Co. 

1883. 


PREFACE. 


To  open  the  path  to  the  myriad  wonders  of  creation, 
which,  altogether  unseen  by  the  unassisted  eye,  are 
made  cognisable  to  sight  by  the  aid  of  the  micro- 
scope, is  the  aim  and  scope  of  this  volume.  Great 
and  gorgeous  as  is  the  display  of  Divine  power  and 
wisdom  in  the  things  that  are  seen  of  all,  it  may 
safely  be  affirmed  that  a  far  more  extensive  prospect 
of  these  glories  lay  unheeded  and  unknown,  till  the 
optician's  art  revealed  it.  Like  the  work  of  some 
mighty  genie  of  Oriental  fable,  the  brazen  tube  is 
the  key  which  unlocks  a  world  of  wonder  and  beauty 
before  invisible,  which  one  who  has  once  gazed  upon 
it  can  never  forget,  and  never  cease  to  admire. 

This  volume  contains  but  a  gleaning  :  the  author 
has  swept  rapidly  across  the  vast  field  of  marvels, 
snatching  up  a  gem  here  and  there,  and  culling  one 
and  another  of  the  brilliant  blossoms  of  this  flowery 
region,  to  weave  a  specimen  chaplet,  a  sample  coronal, 
which  may  tell  of  the  good  things  behind.  Yet  the 
selection  has  been  so  made  as  to  leave  untouched  no 
considerable  area  of  the  great  field  of  Zoology  which 
is  under  the  control  of  the  microscope  ;  so  that  the 
student  who  shall  have  verified  for  himself  the  obser- 
vations here  detailed,  will  be  no  longer  a  tyro  in 


IV  PEEPACE. 

microscopic  science,  and  will  be  well  prepared  to 
extendhis  independent  researches,  without  any  other 
limit  than  that  which  the  finite,  though  vast,  sphere 
of  study  itself  presents  to  him. 

The  staple  of  the  work  now  offered  to  the  public 
consists  of  original  observation.  The  author  is  far 
from  thinking  lightly  of  the  labours  of  others  in  this 
ample  field ;  but  still,  it  is  true,  that  respecting  very 
many  of  the  subjects  that  came  under  his  notice,  he 
found,  in  endeavouring  to  reproduce  and  verify  pub- 
lished statements,  so  much  perplexity  and  difficulty, 
that  he  was  thrown  back  upon  himself  and  nature, 
compelled  to  observe  de  novo,  and  to  set  down 
simply  what  he  himself  could  see.  The  ever- 
accumulating  stock  of  observed  and  recorded  facts 
is  the  common  property  of  science ;  and  the  author 
has  not  scrupled  to  reproduce,  to  amplify,  or  to 
abridge  his  own  observations  which  have  already 
appeared  in  his  published  works  and  scientific 
memoirs,  as  freely  as  he  would  have  cited  those  of 
any  other  observer  in  which  he  had  confidence,  and 
which  were  germane  to  his  purpose.  Yet,  in  almost 
all  cases,  the  observations  so  used  have  been  sub- 
jected to  renewed  scrutiny,  and  have  been  verified 
afresh,  or  corrected  where  found  defective. 

In  order  to  relieve  as  much  as  possible  the  dryness 
of  technical  description,  a  colloquial  and  familar  style 
has  been  given  to  the  work ;  which  has  been  thrown 
into  the  form  of  a  series  of  imaginary  conversaziones, 
or  microscopical  soirees,  in  which  the  author  is  sup- 
posed to  act  as  the  provider  of  scientific  entertain- 
ment and  instruction  to  a  circle  of  friends.  It  is 
proper  to  add,  however,  that  the  precision  essential 


PREFACE.  V 

to  science  has  never  been  consciously  sacrificed.  A 
master  may  be  easy  and  familiar  without  being  loose 
or  vague. 

A  considerable  amount  of  information  will  be 
found  incidentally  scattered  throughout  the  work  on 
microscopic  manipulation, — the  selecting,  securing, 
and  preparing  of  the  objects  for  examination  ; — an 
important  matter,  and  one  which  presents  a  good 
deal  of  practical  difficulty  to  the  beginner.  Not  a 
little  help  will  be  afforded  to  him,  also,  on  the  power 
to  observe  and  to  discriminate  what  he  has  under  his 
eye.  In  almost  every  instance,  the  objects  selected 
for  illustration  are  common  things,  such  has  any  one 
placed  in  tolerably  favourable  circumstances,  with 
access  to  sea-shore  and  country-side,  may  reasonably 
expect  to  meet  with  in  a  twelvemonth's  round  of 
research. 

The  pictorial  illustrations  are  almost  co-extensive 
with  the  descriptions ;  they  are  one  hundred  and 
thirteen  in  number;  all,  with  the  exception  of 
eighteen,*  productions  of  the  author's  own  pencil, 
the  great  majority  having  been  drawn  on  the  wood 
direct  from  the  microscope,  at  the  same  time  as  the 
respective  descriptions  were  written.  He  ventures 
to  hope  that  they  will  be  found  accurate  delineations 
of  the  objects  represented. 

TORQUAY,  February,  1859. 


*  The  subjects  on  pp.  43,  48,  98,  100,  and  151,  have  been  copied, 
inder  the  courteous  permission  of  the  publisher,  from  Dr.  Carpenter's 
valuable  work,  "  The  Microscope,  and  its  Revelations."  (Churchill, 
London.) 


PREFACE  TO  THE  PRESENT  EDITION. 


IN  preparing  a  new  edition  of  this  Work  for  the  press, 
every  page  has  passed  under  the  Author's  eye,  and 
has  been  examined  with  earnest  care.  A  very  large, 
portion  of  it  consisting  of  his  own  original  re- 
searches, there  was  little  room  for  alteration ;  but 
new  facts,  interesting  in  themselves,  and  germane  to 
the  subjects  herein  treated,  which  have  been  recorded 
since,  he  has  used  to  enrich  the  work.  These  have 
been  uniformly  added  in  the  shape  of  marginal 
notes ;  leaving  the  text  untouched,  a  reflection  of 
Microscopical  Science  fifteen  years  ago. 

P.  H.  G. 

TORQUAY,  Jan.  1874. 


CONTENTS. 


CHAPTER  I. 
HAIRS,  FEATHERS,  AND  SCALES  . 


CHAPTER  II. 
BLOOD 25 

CHAPTER  III. 

MOLLUSCA  :   THEIR  SHELLS,  TONGUES,  EYES,  AND  EARS        .  .         39 

CHAPTER  IV. 
SEA-MATS  AND  SHELLY  CORALLINES 59 

CHAPTER  V. 
INSECTS  :  WINGS  AND  THEIR  APPENDAGES 70 

CHAPTER  VI. 
INSECTS  :  THEIR  BREATHING  ORGANS  ......      93 

CHAPTER  VII. 
INSECTS  :  THEIR  FEET "...    109 

CHAPTER  VIII. 

INSECTS  :  STINGS  AND  OVIPOSITORS     .       .       .       .  .125 

CHAPTER  IX. 
INSECTS:  THEIR  MOUTHS     .        .  138 


Vlll  CONTENTS. 

PAGE 

CHAPTER  X. 
INSECTS  :  THEIR  EARS  AND  EYES 158 

CHAPTER  XL 
CRABS  AND  SHRIMPS 171 

CHAPTER  XII. 
BARNACLES.        .        .    .« '.,,  ,.   . .' 191 

CHAPTER  XIII. 
SPIDERS  AND  MITES     . 203 

CHAPTER  XIV. 
WHEEL-BEARERS  .    • 223 

CHAPTER  XV. 
WORMS.        ...'«.        .        .        .        .        .        .        .258 

CHAPTER  XVI. 
SEA-URCHINS  AND  SEA-CUCUMBERS 276 

CHAPTER  XVII. 
JELLY-FISHES       .,;..•', 307 

CHAPTER  XVIII. 
ZOOPHYTES  .       »        .        . 325 

CHAPTER  XIX. 
SEA-ANEMONES  :  THEIR  WEAPONS 355 

CHAPTER  XX, 
PROTOZOA  AND  SPONGES 376 

CHAPTER  XXI. 

INFUSORIA    .  .    389 


LIST  OF  ILLUSTRATIONS. 


PAGE 

HUMAN  HAIR 2 

HOG'S  BRISTLE 5 

FIBRE  OF  SHEEP'S  WOOL 7 

HAIR  OP  CAT 8 

HAIRS  OF  MOLE 9 

HAIR  OF  SABLE 9 

HAIR  OF  MOUSE       . 10 

TIP  OP  SMALL  HAIR  OF  MOUSE 11 

HAIR  OF  BAT   .       .       .       .       .        .        .        .       .        .        .11 

HAIR  OP  INDIAN  BAT 12 

TIP  OP  HAIR  OP  DERMESTBS  .       . 14 

BARB  OF  CLOTHING  FEATHER  OF  FOWL       .    •    .       .       .       .15 

BARB  FROM  GOOSI-QUILL 16 

SCALES  OF  PERCH 17 

SCALES  OF  GOLD-FISH 19 

SCALE  OF  FLOUNDER 21 

SCALES  OF  PIKE       . 23 

SPICULA  OF  GOLD-FISH'S  SCALE 24 

BLOOD  DISKS 28 

CIRCULATION'  IN  FROG'S  FOOT 32 

PEROPHORA 33 

CUTTLE-SHELL 41 

SECTION  OF  NACRE  FROM  PEARL  OYSTER 43 

TONGUE  OF  TROCHUS 48 

STRUCTURE  OF  EYE  IN  SNAIL 54 

LEAFY  SEA-MAT 62 

DOUBLING  AND  HOOKS  IN  A  BEE'S  WIXG     .....  74 

SCALES  ON  A  GNAT'S  WING    .               75 


X  LIST    OF    ILLUSTRATIONS. 

PAGE 

BRISTLE-TAIL 76 

SCALE  OP  BRISTLE-TAIL 77 

BATTLEDORE-SCALE  OP  POLYOMMATUS  ALEXIS    ....  80 

FRINGED  SCALE  OP  PIERIS 81 

SCALES  OP  DIAMOND-BEETLE 83 

AIR-PIPE  OP  FLY 95 

SPIRACLE  OF  FLY 98 

SPIRACLE  OP  LEATHER-COAT 99 

SPIRACLE  OP  COCKCHAFER- GRUB 100 

GRUB  OP  CHAMELEON  FLY    .       .       .       .       .       .       .       .102 

FOOT  OP  FLY 116 

FOOT  OF  WATER-BEETLE       .  .     \       .       .       .       .118 

STING  OF  BEE 127 

GALL-FLY,  AND  MECHANISM  OF  OVIPOSITOR      .       .       .       .128 

OUTER  SAW  OP  SAW-FLY .133 

INNER  SAW  OF  SAW-FLY      ........  134 

MOUTH  OF  BEETLE 140 

JAWS  OF  BEE 142 

LANCETS  OF  FEMALE  GNAT 150 

TONGUE  OF  BLOW-FLY 151 

SUCKER  OF  BUTTERFLY 156 

ANTENNA  OF  COCKCHAFER 162 

ANTENNA  OF  OAK  EGGER  MOTH 164 

EAR  OP  CRAB. 172 

DAPHNIA.       .       .      V 179 

CYPRIS     . 181 

ZOEA  OF  SHORE-CRAB    . 183 

SECOND  STAGE  OF  SHORE-CRAB 185 

THIRD  STAGE  OF  SHORE-CRAB     ; 187 

ADULT  SHORE-CRAB 188 

HAND  OF  BARNACLE 193 

YOUNG  OF  BARNACLE 197 

FANG  OF  SPIDER 206 

EYES  OF  SPIDER .207 

CLAWS  OP  SPIDER 217 

HEAD  OF  CHEESE-MITE 221 

BRACHIONUS 232 

MOUTH  OF  BRACHIONUS  .                                                           .  235 


LIST    OF    ILLUSTRATIONS.  XI 

PACK 

WHIPTAIL «       ....  288 

SKELETON  WHEEL-BEAKER 2-43 

SWORD-BEARER 247 

TRIPOD  WHEEL-BEARER 249 

TWO-LIPPED  TUBE-WHEEL 252 

WHEELS  OP  TUBE-WHEEL 253 

FOOT  OP  NAIS 262 

THROAT  OF  LEECH  LAID  OPEN     .       .       .       .       »       .       .  269 

JAW  OF  LEECH 270 

PUSHING-POLES  OF  SERPULA 273 

HOOKS  OF  SERPULA 274 

SPIXE  OF  ECHINUS 281 

HEAD  OF  PBDICELLARIA  TRIDENS 284 

SUCKER  OF  URCHIN 289 

PORES  OF  URCHIN 289 

SUCKER-PLATE  OF  URCHIN 292 

DUMB-BELLS  IN  HOLOTHURIA 298 

WHEEL  IN  CHIRODOTA 298 

ANCHOR- PLATE  IN  SYNAPTA 299 

LARVA  OF  SEA-URCHIN 303 

YOUNG  SEA-URCHIN  :  DEVELOPMENT  OF  DISK    .       .       .       .305 

CYDIPPE  .       .       .       % 310 

SARSIA 316 

THAUMANTIAS. 319 

OTOLITHES  OF  THAUMANTIAS 320 

TURRIS  AND  ITS  YOUNG 324 

LAOMEDEA 328 

TENTACLE  OF  LAOMEDEA 329 

STAURIDIA '     .       .342 

LARES 345 

POLYPES  OF  Cow's  PAP 351 

SPICULA  OF  Cow's  PAP 353 

PORTION  OF  ACONTIUM 357 

CINCLIDES 358 

CNIDA  OF  MADREPORE 364 

CNIDA  OF  TEALIA 367 

CMDA  OF  CORYNACTIS 370 

FORMS  OF  AMCEBA  .                                                                .  379 


xii  LIST    OF   ILLUSTRATIONS. 

PAGE 

SECTION  OP  SPONGE 386 

THREK-SIDED  EUGLENA * 

SWAN-NECK  AND  ITS  DIVISIONS 394 

PARAMtECIUM 398 

COLEPS  AND  CHILOMONAS 3" 

VORTICELLJS 402 

ACINETA 4°' 

VAGINICOLA ^ 

EUPLOTES 416 


EVENINGS 

AT   THE   MICEOSCOPE, 


CHAPTER  I. 

* 

HAIRS,  FEATHEBS,  AND  SCALES. 

NOT  many  years  ago  an  eminent  microscopist  received  a 
communication  inquiring  whether,  if  a  minute  portion  of 
dried  skin  were  submitted  to  him,  he  could  determine  it  to 
be  human  skin  or  not.  He  replied  that  he  thought  he 
could.  Accordingly  a  very  minute  fragment  was  for- 
warded to  him,  somewhat  resembling  what  might  be  torn 
from  the  surface  of  an  old  trunk,  with  all  the  hair  rubbed 
off. 

The  professor  brought  his  microscope  to  bear  upon  it, 
and  presently  found  some  fine  hairs  scattered  over  the 
surface ;  which,  after  carefully  examining  them,  he  pro- 
nounced with  confidence  to  be  human  hairs,  and  such  as 
grew  on  the  naked  parts  of  the  body ;  and  declared  the 
person  who  had  owned  them  to  have  been  of  a  fair  com- 
plexion. 

This  was  a  very  interesting  decision,  because  the  frag- 
ment of  skin  was  taken  from  the  door  of  an  old  church  in 
Yorkshire ;  *  in  the  vicinity  of  which  a  tradition  is  pre- 

*  I  am  writing  from  memory,  having  no  means  of  referring  to  the 
original  record,  which  will  be  found  in  the  first  (or  second)  volume  of 
the  "Transactions  of  the  Microscopical  Society"  of  London.  The 
general  facts,  however,  may  be  depended  on. 

B 


2  EVENINGS    AT    THE    MICROSCOPE. 

served,  that,  about  a  thousand  years  ago,  a  Danish  robber 
had  violated  this  church,  and,  having  been  taken,  had  been 
condemned  to  be  flayed,  and  his  skin  nailed  to  the  church- 
door,  as  a  terror  to  evil-doers.  The  action  of  the  weather 
and  other  causes  had  long  ago  removed  all  traces  of  the 
stretched  and  dried  skin,  except  that,  from  under  the 
edges  of  the  broad-headed  nails  with  which  the  door  was 
studded,  fragments  still  peeped  out.  It  was  one  of  those 
atoms,  obtained  by  drawing  one  of  the  old  nails,  that  was 
now  subjected  to  microscopical  scrutiny ;  and  it  was  interest- 
ing to  find  that  the  wonder-showing  tube  could  confirm  the 
tradition  with  the  utmost  certainty  ;  not  only  in  the  general 
fact,  that  it  was  really  the  skin  of  man,  but  in  the  special 
fact  of  the  race  to  which  that  man  belonged,  viz.,  one  with 
fair  complexion  and  light  hair,  such  as  the  Danes  are  well 
known  to  possess. 

It  is  evident  from  this  anecdote  that  the  human  hair 
presents  characters  which  are  so  indelible  that  centuries  of 
exposure  do  not  avail  to  obliterate  them,  and 
which  readily  distinguish  it  from  the  hair  of 
any  other  creature.  Let  us  then  begin  our 
evening's  entertainment  by  an  examination  of 
a  human  hair,  and  a  comparison  of  it  with 
that  which  belongs  to  various  animals. 

Here,  then,  is  a  hair  from  my  own  head.  I 
cut  off  about  half-an-inch  of  its  length,  and, 
laying  it  between  two  plates  of  glass,  put  it 
upon  the  stage  of  the  microscope.  I  now 
apply  a  power  of  600  diameters ;  that  is,  the 
apparent  increase  of  thickness  is  the  same 
as  if  six  hundred  of  these  hairs  were  placed 
side  by  side.  Now,  with  this  eye-piece  micro- 
meter, we  will  first  of  all  measure  its  diameter. 
You  see,  crossing  the  bright  circular  field  of 
HAIR,  view,  a  semi-pellucid  cylindrical  object ;  that 
is  the  hair.  You  see  also  a  number  of  fine 


HAIRS,    FEATHEBS,    AND    SCALES.  3 

lines  drawn  parallel  to  each  other,  exactly  like  those  on 
an  ivory  rule  or  scale,  with  every  fifth  line  longer  than  the 
rest,  and  every  tenth  longer  still.  This  is  the  micrometer, 
or  scale  by  which  we  measure  objects ;  and  the  difference 
in  the  length  of  the  lines,  you  will  readily  guess,  is  merely 
a  device  to  facilitate  the  counting  of  them.  By  moving 
the  stage  up  or  down,  or  to  either  side,  we  easily  bring 
the  hair  exactly  into  the  centre  of  the  field;  and  now, 
by  adjusting  the  eye-piece,  we  make  the  scale  to  lie 
directly  across  the  hair,  at  right  angles  with  its  length. 
Thus  we  see  that  its  diameter  covers  just  thirty  of  the 
fine  lines ;  and  as,  with  this  magnifying  power,  each 
line  represents  1-10, 000th  of  an  inch,  the  hair  is  30- 
10,OOOths,=z:T^rd  of  an  inch,  in  diameter. 

In  all  branches  of  natural  history,  but  perhaps  pre- 
eminently in  microscopic  natural  history, — owing  to  its 
greater  liability  to  error  from  deceptive  appearances, — we 
gain  much  information  on  any  given  structure  by  com- 
paring it  with  parallel  or  analogous  structures  in  other 
forms.  Thus  we  shall  find  that  our  understanding  of  the 
structure  of  this  hair  will  be  much  increased  when  we  have 
seen,  under  the  same  magnifying  power,  specimens  of  the 
hair  of  other  animals.  In  order,  however,  to  explain  it,  I 
must  anticipate  those  observations. 

What  we  see,  then,  is  a  perfectly  translucent  cylinder, 
having  a  light  brown  tinge,  and  marked  with  a  great 
number  of  delicate  lines,  having  a  general  transverse 
direction,  but  very  irregularly  sinuous  or  winding  in 
their  individual  courses.  These  lines  we  perceive  to  be 
on  the  surface ;  because,  if  we  slowly  turn  the  adjustment- 
screw,  the  lines  grow  dim  on  the  central  part  of  the 
cylinder,  while  those  parts  that  lie  near  the  edges  (speak- 
ing according  to  the  optical  appearance)  come  into  dis- 
tinctness. Presently  the  edges  of  the  cylinder  become 
sharply  defined,  and  are  seen  to  be  cut  into  exceedingly 
shallow  saw-like  teeth,  about  as  far  apart  as  the  lines; 
B  2 


4  EVENINGS    AT    THE    MICKOSCOPE. 

these,  however,  are  so  slight  that  they  can  be  seen  only 
by  very  delicate  adjustment.  We  go  on  turning  the 
screw,  and  presently  another  series  of  transverse  lines, 
having  the  same  characters  as  the  former,  but  differing 
from  them  individually,  come  into  view,  at  the  sides  first, 
and  presently  in  the  middle,  and  then,  as  we  still  turn, 
become  dim,  and  the  whole  is  confused.  In  fact,  our  eye 
has  travelled,  in  this  process,  from  the  nearer  surface  of 
the  hair,  right  through  its  transparent  substance,  to  the 
farther  surface ;  and  we  have  seen  that  it  is  surrounded 
by  these  sinuous  lines,  which  the  edges — or  those  portions 
of  the  hair  which  would  be  the  edges,  if  it  were  split 
through  the  middle  (for,  optically,  this  is  the  same  thing) 
— show  to  be  successive  coats  of  the  surface,  suddenly 
terminated.  If  we  suppose  a  cylinder  to  be  formed  of  very 
thin  paper,  rolled  up,  and  then,  by  means  of  a  turning- 
lathe,  this  cylinder  to  be  tapered  into  a  very  lengthened 
cone,  the  whole  would  be  surrounded  by  lines  marking  the 
cut-through  edges  of  the  successive  layers  of  paper ;  and, 
owing  to  the  thickness  of  the  paper  not  being  mathe- 
matically equal  in  every  part,  these  edges  would  be 
sinuous ;  exactly  as  we  see  in  these  lines  upon  the  hair. 
The  effect  and  the  cause  are  the  same  in  the  two  cases. 

A  hair  is  closely  analogous  to  the  stem  of  a  plant; 
inasmuch  as  it  grows  from  a  root,  by  continual  additions  of 
cells  to  the  lower  parts,  which,  as  they  lengthen,  push 
forward  the  ever-extending  tip.  Indeed,  in  some  of  the 
hairs  which  we  shall  presently  look  at,  there  is  the  most 
curious  resemblance  to  the  stem  of  a  palm,  with  the  pro- 
jections produced  by  the  successive  growth  and  breaking 
away  of  leaf-bases  around  the  central  cylinder.  Inter- 
nally, too,  the  resemblance  is  remarkable ;  for,  if  we 
split  a  human  hair,  and  especially  if  we  macerate  it,  i.e. 
soften  it  by  soaking  it,  in  weak  muriatic  acid,  we  shall 
find  it  composed  of  (1)  a  thin  but  dense  kind  of  bark, 
forming  the  successive  overlapping  scales  just  described ; 


HAIRS,  FEATHERS,  AND  SCALES.  5 

(2)  a  fibrous  substance,  extending  from  the  bulb  to  the 
point  of  the  hair.  By  soaking  the  hair  in  hot  sulphuric 
acid,  this  fibrous  substance  resolves  itself  into  an  immense 
number  of  very  long  cells,  pointed  at  each  end,  and 
squeezed  by  mutual  pressure  into  various  angular  forms. 
"  A  human  hair,  of  one-tenth  of  a  line  in  thickness,*  has 
about  250  fibrils  in  its  mere  diameter,  and  about  50,000 
in  its  entire  calibre :  so  that  these  ultimate  fibrils  are 
finer  than  those  of  almost  any  other  known  tissue,  from 
the  great  elongation  and  narrowing  of  their  constituent 
cells  as  they  are  drawn  out  into  the  shaft  of  the  hair 
during  growth ;  and  hence  the  expanded  bulb  of  the  hair, 
where  the  cells  are  yet  spherical  and  soft."t  (3)  Running 
through  the  very  centre  of  the  fibrous  portion  may  be 
sometimes  discerned  a  dark  slender  line,  which  is  a  sort  of 
pith  (medulla)  composed  of  minute  roundish  cells,  filled 
with  air,  and  arranged  in  two  or  three  rows.  J 


HOO'fl  BRISTLES. 

The  bristles  of  the  Hog  bear  much  resemblance  to  the 
human  hair.  On  this  slide  is  one  (a),  which  you  perceive 

*  This  is  nearly  thrice  as  great  as  the  diameter  I  have  given  above, 
which  is  the  result  of  several  careful  admeasurements  of  different 
hairs,  taken  from  childhood  and  adult  age. 

t  Grant,  "  Outl.  Comp.  Anat.,"  647. 

J  "  The  cortical  (or  bark-like)  substance  has  different  colour,  accord- 
ing to  the  colour  of  the  hair ;  generally,  the  colour  is  diffused  through 
its  whole  mass ;  less  frequently,  the  colour  depends  on  granular  pigment 
scattered  through  its  substance  in  small  masses.  The  cortical  substance 


6  EVENINGS    AT    THE    MICROSCOPE. 

is  just  thrice  as  thick  as  the  hair  that  we  have  been 
examining,  or  j-J-^th  of  an  inch  in  diameter.  The  sinuous 
lines  across  the  surface  are  proportionally  far  finer  and 
closer  together,  and  no  saw-teeth  are  visible  at  the  edge, 
the  most  delicate  adjustment  showing  only  a  minute  undu- 
lation in  the  outline ;  that  is  to  say,  the  overlapping  scales 
are  far  thinner,  and  therefore  their  terminations  are 
nearer  together,  in  the  hair  of  the  Swine  than  in  that  of  Man. 
I  will  now  show  you  a  transverse  section  of  a  similar 
bristle,  which  I  will  obtain  thus :  I  take  this  old  brush, 
and  with  a  razor  cut  off  one  of  the  bundles  of  bristles, 
close  to  the  wood ;  then  I  take  off  as  thin  a  shaving  as 
I  can  cut,  wood,  bristles,  and  all :  I  repeat  the  same  opera- 
tion two  or  three  times.  Now,  paving  picked  out  the 
shavings  of  wood,  I  take  up  with  the  point  of  my  pen- 
knife a  few  of  the  dust-like  atoms  that  remain,  and  scatter 
them  on  this  plate  (or  slide)  of  glass,  and  these  I  cover 
with  another  plate  of  thin  glass  ;  for  this  dust  is  composed 
of  thin  transverse  slices  of  the  bristles,  and  as  I  scatter 


contains  a  number  of  cavities  filled  with  air,  most  evident  in  the  hair 
from  aged  persons,  or  in  dry  hair. 

"  The  central  portion,  the  medulla,  forms,  when  well  developed,  an 
axis- cylinder,  one-fifth,  or  one-fourth,  the  diameter  of  the  hair,  with 
sharp  outlines,  generally  central,  but  often  a  little  excentric  in  position. 
It  is  often  wanting  in  human  hair,  especially  in  blond  hair.  ...  In 
woolly  hair  it  is  always  wanting ;  also  in  the  hair  of  the  new-born 
child.  The  medullary  substance  is  often  interrupted,  and  sometimes 
consists  of  only  a  few  dark  points  lying  in  the  axis  of  the  hair  .  .  . 
The  medullary  substance  has  been  thought  to  contain  the  pigment :  this 
is  not  so,  the  supposed  pigment-granules  being  very  minute  air-bubbles. 
The  cause  of  the  colour  of  the  hair  is  found  in  the  diffuse  pigmentation 
of  the  cortical  substance.  The  cause  for  the  hair  becoming  grey  or 
white  is  to  be  found  in  the  disappearance  of  the  diffuse  pigmentation 
of  the  cortical  substance,  the  cause  of  which  is  not  yet  known.  The 
medullary  substance  can  be  more  easily  seen  in  white  hair  than  in 
coloured."  (From  a  valuable  memoir,  entitled,  "  Hair  in  its  Micro- 
scopical and  Medico-legal  Aspects,"  by  Dr.  E.  Hofman ;  transferred  to 
the  "  English  Mechanic "  for  May  9,  1873,  from  the  "  New  York 
Medical  Journal.") 


HAIRS,    FEATHERS,    AND    SCALES.  7 

them,  some  will  fall  upon  their  cut  ends,  so  that  we  shall 
look  through  them  endwise. 

Here  is  one,  very  suitable  for  examination  (6), — since  it 
is  not  a  whole  section,  the  razor  having  passed  somewhat 
obliquely  across  it,  coming  out  beyond  the  middle,  where  it 
thins  away  to  an  edge.  The  outline  is  not  circular,  but 
elliptical;  that  is,  the  hair  is  not  round,  but  flattened. 
There  is  no  separable  cortex,  or  bark,  and  the  whole  sub- 
stance appears  as  if  made  up  of  exceedingly  fine  fibres,  of 
which  we  see  the  ends  cut  across.  A  rough  dark  line 
occupies  the  middle  of  the  slice,  in  the  plane  of  the 
greater  diameter ;  but  at  the  edge  of  the  slice  we  are  able 
to  see  that  this  is  not  a  solid  core,  as  has  been  sometimes 
supposed,  but  a  cavity  passing  up  through  the  hair.  It  is 
surrounded  by  a  layer  of  cells,  called  medullary,  and 
which  appear  black,  because  they  are  filled  with  air. 

The  finer  hairs  of  the  Horse  and  the  Ass,  such 
as  those  selected  from  the  cheeks,  have  the 
sinuous  edges  of  the  plates  about  as  close  as 
in  human  hair.  But  they  are  distinguished  at 
once  by  the  conspicuousness  of  the  medullary 
portion,  which  is  thick,  and  quite  opaque, 
and  is  broken  up  (especially  towards  each  ex- 
tremity of  the  hair)  into  separate  longitudinal 
irregular  masses. 

The  fine  wool  of  the  Sheep  is  clothed  with 
imbrications/"  proportionally  much  fewer  than 
those  of  human  hair,  while  the  diameter  is 
also  much  less.  Thus  these  examples,  selected 
from  fine  flannel  and  from  coarse  worsted, 
vary  in  diameter  from  ^oV^th  to  -^th  of  an 
inch ;  and  there  are,  upon  an  average,  about 
two  imbrications  in  a  space  equal  to  the  dia-  FIBRB  OP 
meter.  No  colour  is  perceptible  in  these  spe-  8HEEP'S  WOOL- 

*  A  structure  is  said  to  be  imbricated  when  it  is  arranged  like  tiles 
on  the  roof  of  a  house. 


8  EVENINGS   AT   THE    MICROSCOPE. 

cimens ;  they  are  as  transparent  and  colourless  as  glass. 
The  imbricated  plates  project  here  considerably  more  than 
in  either  of  the  examples  we  before  examined ;  the 
"  teeth,"  however,  form  an  obtuse  angle. 

We  shall  presently  see  the  importance  of  this  imbri- 
cate structure ;  but  we  will  first  look  at  a  few  more  ex- 
amples, in  which  we  shall  find  it  still  more  strongly  de- 
veloped, in  conjunction  with  some  other  peculiarities.  All 
the  hairs  that  we  have  looked  at  are  what  I  have  called 
fibrous  in  their  interior  texture,  but  those  of  many  animals 
are  more  distinctly  cellular. 

Thus,  in  these  specimens,  plucked  from  the  fur  of  the 
Cat  that  lies  coiled  up  on  the  hearthrug,  we  see,  first,  that 
the  imbrications  are  short,  being  about  equal 
to  the  diameter  in  length,  but  are  very  strongly 
marked ;  though,  like  those  of  the  Sheep's 
wool,  obtuse.  Hence  the  outline  is  extremely 
like  that  of  the  stem  of  an  old  rough  palm- 
tree.  There  is  a  distinct  bark  (cortex),  which 
is  thick,  and  marked  with  longitudinal  lines, 
which  add  to  the  resemblance  just  alluded  to. 
The  interior  is  clear,  marked  off  at  pretty 
regular  intervals  by  the  broad  flattened  me- 
dullary cells,  in  single  series,  each  cell  occu- 
pying, for  the  most  part,  the  whole  breadth 
of  the  interior.  These  cells  are  transparent, 
and  apparently  empty  ;  but  their  walls  ap- 
,  pear  opaque  and  almost  black, — an  optical 
illusion,  dependent  on  the  absorption  of  the 
light  by  their  surfaces  at  certain  angles  with 
the  eye  of  the  beholder.  The  fibrous  portion  is  here 
almost  displaced  by  the  great  development  of  the  medul- 
lary cells. 

In  the  larger  hairs  of  the  Mole,  which  we  will  now  look 
at,  the  bark  is  very  thin  ;  and  though  the  surface  is 
marked  with  sinuous  lines,  these  do  not  project  into  teeth. 


HAIRS,  FEATHERS,  AND  SCALES. 


9 


HAIES   OF   MOLE. 


The  pith  here  again  forms  the  greater  portion  of  the  hair, 
the  cells  of  which  it  is  composed  being  placed  in  single 
series,  which,  for  the  most  part, 
extend  all  across  the  body  of 
the  hair,  though  they  are  some- 
what irregular  both  in  size 
and  shape.  They  are  rather 
flattened,  and  appear  per- 
fectly black  (that  is,  opaque) 
by  transmitted  light,  their  sur- 
faces absorbing  all  the  rays  of 
light.  The  small  hairs  of  the 
same  animal,  however,  are  very 
different  in  form :  they  are 
flattened,  so  as  to  appear  twice 
as  broad  in  one  aspect  as  in 
another  at  right  angles  to  it; 
and,  what  is  curious,  the 

scales  of  the  bark  project  into  strongly-marked  imbrica- 
tions on  one  side,  and  are  scarcely  perceptible  on  the 
other.  Here,  as  in  the  larger  hairs,  there  is  a  single  row 
of  oval  transverse  cells,  perfectly  opaque. 

The  hair  of  many  of  the 
smaller  Mammalia  shows 
considerable  diversity  of 
form,  according  to  the  part 
which  we  select  for  observ- 
ation. Thus,  if  we  take 
a  long  hair  out  of  this 
Sable  tippet,  and  examine 
it  near  the  base,  we  see 
(a)  that  it  is  very  slender,  a| 
transparent,  and  colour- 
less, covered  with  strongly- 
marked  imbrications,  which 
are  not  obtuse  teeth,  but 

HAIB  OF    SABLE. 


10 


EVENINGS    AT    THE    MICROSCOPE. 


long,  pointed,  overlapping  scales,  about  ten  of  which 
form  a  complete  ring,  or  whorl,  as  it  is  called.  The 
fibrous  portion  is  moderately  thick ;  inclosing  a  wide 
pith  of  roundish  cells,  set  in  two  rows,  that  allow  the 
rays  of  light  to  be  transmitted  through  their  central 
parts. 

As  we  trace  the  hair  upwards  (6),  by  moving  the 
stage  of  the  microscope,  by-and-by  it  swells  and 
rapidly  increases  in  thickness  ;  the  imbrications  are 
scarcely  perceptible ;  while  the  pith-cells  have  greatly 
augmented  in  number  and  in  breadth.  These  are  ar- 
ranged in  confused  close-set,  transverse  rows,  and  are 
nearly  opaque. 

Still  tracing  up  the  same  hair,  as  we  approach  the  tip, 
the  bark  and  fibrous  part  become  very  thin  ;  the  cells  are 
fewer  and  fewer  till  they  cease  altogether,  and  a  long 
slender  point,  of  a  clear  yellow  tinge,  without  cells,  pre- 
sents transverse  wavy  lines  of  imbrication  scarcely  pro- 
jecting. 

The  hair  of  the  common  Mouse  is  a  pretty  and  inter- 
esting object.  In  the  larger  speci- 
mens the  fibrous  portion  is  reduced 
almost  to  nothing.  The  imbrica- 
tions project  very  little,  but  care- 
ful observation  reveals  slanting 
lines  proceeding  from  the  "teeth;" 
which  show  that  the  whole  surface 
is  clothed  with  large  pointed  scales, 
which  are  very  thin,  and  lie  close. 
The  pith  consists  of  large  flattened 
cells,  arranged  thus :  one  row 
passes  up  through  the  centre,  and 
other  similar  ones  are  set  in  a 
circle  around  it,  so  that  a  longitudi- 
nal section  would  show  three  paral- 
lel rows.  These  cells  are  translucent,  and  some  of  them 


HAIR    OP    MOUSE. 


HAIRS,  FEATHERS,  AND  SCALES.  11 

are  either  wholly  or  partially  lined  with  a  clear  yellow 
pigment,  or  colouring  matter. 

The  smaller  hairs  from  the  same  little  animal 
are  scarcely  distinguishable  from  those  of  the  Cat, 
already  described,  except  that  the  imbrications  are 
proportionally  larger.  In  all,  the  extremity  is  drawn 
out  to  a  lengthened  fine  point,  and  is  occupied  with 
clear  yellow  cells,  except  the  very  tip,  which  is 
colourless,  and  imbricated  with  sinuous  whorls,  each 
consisting  of  a  single  scale. 

But  it  is  in  the  Bats  that  the  imbricated 
character  attains  its  greatest  development. 
On  this  slide  is  a  number  of  hairs  from  the 
fur  of  one  of  our  English  Bats,  in  which  it  is 
far  more  conspicuous  than  in  any  example 
we  have  yet  seen.  In  the  middle  portion  of 
each  hair  the  scales  lie  close,  embracing  their 
successors  to  the  very  edges,  or  nearly;  but 
the  lower  part,  which  is  more,  slender,  re- 
sembles a  multitude  of  trumpet-shaped  flowers 
formed  into  a  chain,  each  being  inserted  into 
the  throat  of  another.  The  lip  of  the  "  flower  "  tit 
is  generally  oblique,  and  here  and  there  we 
can  perceive  that  each  is  formed  of  two  half- 
encircling  scales ;  for  one  scale  occasionally 
•  springs  from  the  level  of  its  fellow,  so  as  to  OF  BAT. 
make  the  imbrication  alternate. 

Even  this,  however,  is  far  excelled  by  a  species  of  Bat 
from  India,  of  whose  hair  I  have  now  specimens  on  the 
stage.  The  trumpet-like  cups  are  here  very  thin  and 
transparent,  but  very  expansive  ;  the  diameter  of  the  lip 
being,  in  some  parts  of  the  hair,  fully  thrice  as  great  as 
that  of  the  stem  itself.  The  margin  of  each  cup  appears 
to  be  undivided,  but  very  irregularly  notched  and  cut.  In 
the  middle  portion  of  the  hair,  the  cups  are  far  more 
crowded  than  in  the  basal  part,  more  brush-like,  and  less 


HAIR 

OF 
MOVSE 


12 


EVENINGS    AT    THE    MICROSCOPE. 


xV 


1 


\  f 


t 


t 


elegant ;  and  this  structure  is  continued  to  the  very 
extremity,  which  is  not  drawn  out  to  so  attenuated  a  point 
as  the  hair  of  the  Mouse,  though  it  is  of  a  needle-like 
sharpness.  The  trumpet- shaped  scales 
are,  it  seems,  liable  to  be  removed  by 
accident ;  for  in  these  dozen  hairs  there 
are  several  in  which  we  see  one  or  more 
cups  rubbed  off,  and  in  one  the  stem  is 
destitute  of  them  for  a  considerable 
space.  The  stem  so  denuded  closely 
resembles  the  basal  part  of  a  Mouse's 
hair  in  its  ordinary  condition. 

This  character  of  being  clothed  with 
overlapping  scales,  each  growing  out  of 
its  predecessor,  is  common,  then,  to  the 
hairs  of  the  Mammalia,  though  it  exists 
in  different  degrees  of  development.  It 
may  be  readily  detected  by  the  unaided 
sense,  even  when  the  eye,  though  as- 
sisted by  the  microscope,  fails  to  recog- 
nise it.  Almost  every  schoolboy  is  familiar  with  the  mode 
by  which  the  tip  of  any  hair  may  be  distinguished  from 
its  base  ;  and,  even  of  the  least  fragment,  the  terminal  end 
from  the  basal  end.  A  hair  is  rubbed  to  and  fro  between 
the  finger  and  thumb,  and  it  regularly  travels  through  in 
the  direction  of  its  base  ;  thus  enabling  the  boy  after  one 
or  two  rubs  to  pronounce  a  very  decided  opinion  on  the 
subject.  Now  you  see  the  cause  of  this  property  lies  in 
the  imbricate  structure ;  the  scales  may  be  ever  so  thin 
and  close,  but  still  they  project  sufficiently  in  any  speci- 
men to  present  a  barrier  to  motion  in  the  direction  of  the 
tip  when  pressed  between  two  surfaces,  such  as  the  fingers, 
while  they  very  readily  move  in  the  opposite. 

But  more  than  the  success  of  a  schoolboy's  magic 
depends  on  the  imbricate  surface  of  hairs.  England's 
time-honoured  manufacture,  that  which  affords  the  highest 


s  ^ 


HAIR  OF  INDIAN  BAT. 


HAIRS,    FEATHERS,    AND    SCALES.  13 

seat  in  her  most  august  assembly,  depends  on  it.  The 
hat  on  your  head,  the  coat  on  your  back,  the  flannel 
waistcoat  that  shields  your  chest,  the  double  hose  that 
comfort  your  ancles,  the  carpet  under  your  feet,  and 
hundreds  of  other  necessaries  of  life,  are  what  they 
are,  because  mammalian  hairs  are  covered  with  sheathing 
scales. 

It  is  owing  to  this  structure  that  those  hairs  which  pos- 
sess it  in  an  appreciable  degree  are  endowed  with  the 
property  of  felting ;  that  is,  of  being,  especially  under  the 
combined  action  of  heat,  moisture,  motion,  and  pressure, 
so  interlaced  and  entangled  as  to  become  inseparable ;  and 
of  gradually  forming  a  dense  and  cloth-like  texture.  The 
"body"  or  substance  of  the  best  sort  of  men's  hats  is 
made  of  lamb's  wool  and  rabbit's  fur,  not  interwoven,  but 
simply  beaten,  pressed,  and  worked  together,  between 
damp  cloths.  The  same  property  enables  woven  woollen 
tissues  to  become  close  and  thick ;  every  one  knows  that 
worsted  stockings  shrink  in  their  dimensions,  but  become 
much  thicker  and  firmer,  after  they  have  been  worn  and 
washed  a  little;  and  the  "stout  broad-cloth,"  which  has 
been  the  characteristic  covering  of  Englishmen  for  ages, 
would  be  but  a  poor,  open,  flimsy  texture,  but  for  the  inti- 
mate union  of  the  felted  wool  fibres,  which  accrues  from 
the  various  processes  to  which  the  fabric  has  been  sub- 
jected. 

In  a  commercial  view,  the  excellence  of  wool  is  tested 
by  the  closeness  of  its  imbrications.  When  first  the  wool- 
fibre  was  submitted  to  microscopical  examination,  the  ex- 
periment was  made  on  a  specimen  of  Merino ;  it  presented 
2,400  little  teeth  in  an  inch.  Then  a  fibre  of  Saxon  wool, 
finer  than  the  former,  and  known  to  possess  a  superior 
felting  power,  was  tried :  there  were  2,720  teeth  in  an 
inch.  Next  a  specimen  of  South-Down  wool,  acknowledged 
to  be  inferior  to  either  of  the  former,  was  examined,  and 
gave  2,080  teeth.  Finally,  the  Leicester  wool,  whose 


EVENINGS   AT    THE   MICROSCOPE. 


felting  property  is  feebler  still,  yielded  only  1,850  teeth 
per  inch.  And  this  connexion  of  good  felting  quality  with 
the  number  and  sharpness  of  the  sheathing  scales,  is  found 
to  be  invariable. 

The  hairs  of  many  insects  are  curious  and  interesting. 
Here  you  may  see  the  head  of  the  hive  bee,  which  is 
moderately  clothed  with  hair;  each  hair  is  slender  and 
pointed,  and  is  beset  with  a  multitude  of  other  short  hairs, 
which  project  from  the  main  stem,  and  stand  out  at  an 
angle  :  these  are  set  on  in  a  spiral  order.  Here,  again,  is 
one  of  the  hinder  legs  of  the  same  bee :  the  yellow  hair, 
which  you  can  see  with  the  naked  eye,  consists  of  strong, 
horny,  curved  spines,  each  of  which  is  scored  obliquely, 
like  a  butcher's  steel.  These  legs  are  used,  as  you  are  well 
aware,  to  brush  off  the  pollen  from  the  anthers  of  flowers, 
wherewith  the  substance  called  bee-bread,  the  food  of  the 
grubs,  is  made :  and  in  this  specimen,  you 
may  see  hundreds  of  the  beautiful  oval  pollen- 
grains  entangled  among  these  formidable-, 
looking  spines. 

These  rusty  hairs  are  from  a  large  cater- 
pillar (that  of  the  Oak  Egger  Moth,  I  be- 
lieve) ;  they  appear,  when  highly  magnified, 
like  stout  horny  rods  drawn  out  to  a  sharp 
point,  and  sending  forth  alternate  short 
pointed  spines,  which  scarcely  project  from 
the  line  of  the  axis. 

But  there  is  scarcely  any  hair  more  curious 
than  that  of  a  troublesome  grub  in  museums 
and  cabinets,  the  larva  of  Dermestes  lardarius, 
which   lives  upon   fur-skins,   and   any   dried 
TIP  OF  HAIR  OF  animal  substances.     It  has  a  cylindrical  shaft, 
DKRMESTES.    which  is  covered  with  whorls  of  large  close-set 
spines,  four  or  five  in  each  whorl,  closely  succeeding  each 
other ;  the  upper  part  of  the  shaft  is  surrounded  by  a 
whorl  of  larger  and  more  knotted  spines,  and  the  extremity 


HAIRS,  FEATHERS,  AND  SCALES. 


15 


is  furnished  with  six  or  seven  large  filaments  or  threads, 
which  appear  to  have  a  knob-like  hinge  in  the  middle,  by 
which  they  are  bent  up  on  themselves. 

The  feathers  of  Birds  are  essentially  hairs.  That 
shrivelled  membrane  which  we  pull  out  of  the  interior  of  a 
quill  when  we  make  a  pen,  is  the  medullary  portion,  dried. 
There  is  a  beautiful  contrivance  in  the  barbs,  or  beards,  of 
most  feathers,  which  I  will  illustrate  by  this  feather  from 
the  body-plumage  of  the  domestic 
fowl.  Every  one  must  have  ob- 
served the  regular  arrangement  of 
the  vane  of  a  feather,  and  the  ex- 
quisite manner  in  which  the  beards 
of  which  it  is  composed  are  con- 
nected together.  This  is  espe- 
cially observable  in  the  wing-fea- 
thers— a  goose-quill  for  example, 
where  the  vane,  though  very  light 
and  thin,  forms  an  exceedingly 
firm  resisting  medium,  the  indi- 
vidual beards  maintaining  their 
union  with  great  tenacity,  and  re- 
suming it  immediately,  when  they 
have  been  violently  separated. 

Now  this  property  is  of  high 
importance  in  the  economy  of  the 
bird.  It  is  essential  that  with 
great  lightness  and  buoyancy — for  the  bird  is  a  flying 
creature — there  be  power  to  strike  the  air  with  a  broad 
resisting  surface.  The  wide  vanes  of  the  quill-feathers 
afford  these  two  requisites,  strength  and  lightness;  the 
latter  depending  on  the  material  employed,  which  is  very 
cellular,  and  the  former  on  the  mode  in  which  the  indivi- 
dual barbs,  set  edgewise  to  the  direction  of  the  stroke, 
take  a  firm  hold  on  each  other. 

Now,  in  the  body-feather,  which  is  under  the  micro- 


BAfcB    OF   CLOTHING  FEATHER 
OF   FOWL. 


16 


EVENINGS    AT    THE    MICROSCOPE. 


scope,  we  see  that  the  central  stem  carries  on  each  side  a 
row  of  barbs,  which  interlock  with  each  other.  The  mag- 
nifying power  shows  us  that  these  barbs  are  not  simple 
filaments,  but  are  themselves  doubly  bearded  in  the  same 
fashion ;  and  further,  that  these  little  beards,  called  bar- 
bules,  of  the  second  series,  are  furnished  with  a  third 
series.  It  is  in  this  third  series  of  filaments,  called  bar- 
bulets,  that  the  tenacity  in  question  resides.  If  we  isolate 
one  of  the  primary  beards,  by  stripping  away  a  few  on 
each  side  of  it,  and  again  put  it  on  the  stage,  we  see  that 
the  secondary  barbules  of  one  side  are  armed  differently 
from  those  of  the  other  side.  Those  of  the  lower  side 
carry  short  and  simple  barbulets,  whereas  those  of  the  side 
which  looks  towards  the  point  of  the  feather  bear  much 
longer  ones ;  and,  moreover,  many  of  them  are  abruptly 
hooked  backwards.  Now,  whenever  the  primary  beards 
are  brought  into  contact,  some  of  these  hooks  catch  on  the 
barbule  next  above,  and,  slipping  into  the  angles  formed 
by  the  barbulets,  hold  there,  and  thus  the  two  contiguous 
beards  are  firmly  locked  together. 

In  the  beard  of  the  goose-quill, 
the  structure  is  essentially  the 
same,  but  the  barbulets  are  far 
more  numerous  and  more  closely 
set;  they  are  also  proportionally 
much  larger — both  those  which 
are  hooked  and  those  which  are 
simple.  Indeed,  the  latter  mani- 
fest a  tendency  to  the  hooked 
form,  and  by  all  these  peculiari- 
ties the  interlocking  power  is  aug- 
mented. It  is  interesting  to  ob- 
serve the  great  expansion  of  the 
beard  in  a  direction  towards  the 
interior  surface  of  the  feather — 
towards  the  stroke,  as  I  just  now 


BARB   FROM   GOOSE-QTJILL. 


HAIRS,  FEATHERS,  AND  SCALES.  17 

observed.  This  is  to  increase  the  resisting  power,  as  a 
thin  board  set  edgewise  will  bear  a  great  weight  without 
bending  or  breaking,  provided  it  can  be  kept  from  yield- 
ing sidewise.  The  barbules  are  arranged  only  on  the  very 
edge,  the  upper  edge,  of  the  beard. 

We  will  now  examine  some  specimens  of  scales  of 
Fishes,  all  of  which  are  very  interesting  and  beautiful  ob- 
jects, under  low  powers  of  the  microscope  ;  though  higher 
powers  are  requisite  to  resolve  their  structure.  We  will 
use  both. 

The  scales  of  almost  all  the  Fishes  with  which  we  are 
familiar,  fall  under  two  kinds,  which  have  been  named 
ctenoid  (or  comb-like),  and  cycloid  (or  roundish).  The 


SCALES   OF    PERCH. 


Perch  affords  us  good  examples  of  the  former  kind.  On 
this  slide  are  three  scales  from  the  body  of  this  fish  :  the 
one  on  the  left  side  is  taken  from  the  back  (a) :  the 
middle  one  from  the  lateral  line  (b) ;  and  the  one  on  the 
right  from  the  belly  (c).  In  order  to  understand  these 
objects,  we  must  remember  that  the  scales  of  Fishes  are 
horny  or  bony  plates,  developed  in  the  substance  of  the 
proper  skin,  with  a  layer  of  which  they  are  always  covered. 
In  most  cases  (as,  for  example,  the  Perch),  the  hinder  end 
of  each  scale  projects,  carrying  with  it  the  thin  layer  of 
skin  with  which  it  is  invested ;  and  thus  the  scales  overlay 
one  another,  like  the  tiles  of  a  house,  or  like  the  feathers 
of  a  bird,  and  that  for  a  like  purpose.  For  as  the  rain, 

c 


18  EVENINGS   AT    THE    MICKOSCOPE. 

falling  on  the  housetop,  has  a  tendency  to  flow  down- 
wards, from  gravitation ;  and  as  the  slope  of  the  roof  is 
in  that  direction,  the  current  passing  over  each  tile  is 
deposited  from  its  bottom-edge  on  the  middle  of  the 
next,  whence  it  still  flows  down  to  the  free  edge, — 
and  so  in  succession.  So  the  motion  of  the  bird  through 
the  air,  and  of  the  fish  through  the  water,  produces  the 
very  same  effect  as  if  these  fluids  were  in  motion,  and  the 
animals  were  still ;  and  therefore  the  bodies  of  the  latter 
are,  as  it  were,  tiled  with  feathers  or  scales,  the  free  edges 
of  which,  looking  in  the  opposite  direction  to  the  coming 
of  the  current  (that  is,  the  same  direction  as  its  flow),  de- 
posit the  successive  particles  of  the  moving  fluid  in  the 
midst  of  the  successive  feathers  or  scales.  Thus  two 
results  ensue,  both  essential  to  the  comfort  of  the  animal : 
first,  the  air  or  water  does  not  run  upward  between  the 
feathers  or  scales  to  the  skin ;  and  secondly,  the  surface 
presents  no  impediment  to  free  motion.  This  latter  ad- 
vantage will  be  appreciated,  if  you  take  hold  of  a  dead  bird 
by  the  legs,  and  push  it  rapidly  through  the  air  tail- 
foremost:  the  feathers  will  instantly  rise  and  ruffle  up, 
presenting  a  powerful  resistance  to  movement  in  that 
direction. 

These  scales  of  the  Perch  have  their  hinder,  or  free 
edge,  set  with  fine  crystalline  points,  arranged  in  succes- 
sive rows,  and  overlapping.  Their  front  side  is  cut  with  a 
scolloped  pattern,  the  extremities  of  undulations  of  the 
surface  that  radiate  from  a  common  point  behind  the 
centre.  These  undulations  are  separated  by  narrow  fur- 
rows, across  which,  contrary  to  the  ordinary  rule,  the 
close-set  lines  that  follow  the  sinuosities  of  the  outline  are 
not  visible.  Under  the  microscope  they  look  as  if  they 
had  been  split  in  these  radiating  lines,  after  the  whole 
number  of  layers  had  been  completed,  and  the  fissures  had 
then  been  filled  with  new  transparent  substance. 

The  middle  scale  is,  as  I  have  said,  from  the  lateral 


HAIBS,    FEATHERS,    AND    SCALES. 


19 


line.  Along  each  side,  in  most  fishes,  may  be  observed  a 
line,  known  as  the  lateral  line,  formed  by  scales  of  peculiar 
form.  They  are  commonly  more  bony  than  the  other 
scales,  and  are  pierced  by  a  tubular  orifice  for  the  escape 
(as  is  generally  supposed,  though  this  has  been  denied)  of 
a  mucous  secretion,  which  is  poured  out  from  glands  be- 
neath, and  thus  flows  over  the  body  for  the  double  purpose 
of  protecting  the  skin  from  the  macerating  influence  of 
the  surrounding  water,  and  of  diminishing  friction  in 
swimming. 

Let  us  now  look  at  some  scales  of  the  cycloid  kind. 
The  great  majority  of  our  fishes  are  clothed  with  such  as 
are  of  this  description.  This  dead  Gold-fish  shall  give  us 
examples.  The  three  scales  in  the  upper  row  are  from 


SCALES  OF  GOLD-FISH. 


the  lateral  line,  the  left-hand  one  (a)  taken  just  behind  the 
head,  the  second  (b)  near  the  middle  of  the  body,  and  the 
right-hand  one  (c)  near  the  tail.  Of  the  lower  row,  the 
first  (d)  is  from  the  back,  the  second  (e)  from  the  middle 
c  2 


20  EVENINGS   AT    THE    MICROSCOPE. 

of  the  belly,  and  the  last  (/)  from  the  throat.  Thus  we 
see  there  is  considerable  variety  in  form  presented  by  the 
scales  even  of  the  same  individual  fish.  They  all,  how- 
ever, differ  from  those  of  the  Perch,  in  this  respect ; — that 
their  free  overlapping  edges  are  entire,  or  destitute  of  the 
crystalline  points  which  we  saw  in  the  former  examples ; 
while  they  agree  in  having  the  front  edges,  by  which  they 
are  during  life  imbedded  in  the  skin,  cut  into  waves  or 
sinuosities.  The  lower  part,  as  we  now  look  at  them,  is 
the  free  portion  of  each,  which  alone  is  visible  in  the  living 
fish,  the  other  parts  being  concealed  by  the  three  neigh- 
bouring scales  that  overlap  it, — above,  in  front,  and  below. 
In  those  from  the  lateral  line,  the  tube  already  referred 
to  is  seen  to  pervade  each,  running  through  it  longitudi- 
nally, so  that  it  opens  behind  on  the  outer  surface,  and  in 
front  on  the  inner  or  under  surface  of  the  scale.  In  the 
scales  near  the  front  of  the  line,  just  behind  the  head,  the 
tube  is  large  and  prominent  (a),  while  in  the  scales  at  the 
opposite  extremity  it  becomes  slender ;  diminishing,  in  the 
very  last  scale,  viz.,  at  the  commencement  of  the  tail-fin,  to 
a  mere  groove. 

The  whole  surface  of  each  scale,  when  viewed  under  a 
lens  of  low  power,  is  seen  to  be  covered  with  concentric 
lines,  following  the  irregular  sinuosities  of  the  outline. 
These  lines  are  the  edges  of  the  successive  layers  of  which 
the  scale  \s  believed  to  be  composed,  each  layer  being 
added  in  the  process  of  growth  to  the  under  surface,  and 
each  being  a  little  larger  every  way  than  its  predecessor ; 
thus  the  scale  is  a  very  depressed  cone,  of  which  the  centre 
is  the  apex.  There  is  a  marked  difference  (indicated  in 
the  figures)  between  that  part  of  the  surface  which  is  ex- 
posed, and  that  which  is  covered  by  the  other  scales  ;  the 
concentric  marks  in  the  former  are  much  coarser  and  less 
regular,  often  being  interrupted,  and  seeming  to  run  into 
each  other,  and  frequently  swelling  into  oval  scars.  This 
may,  perhaps,  be  owing  to  the  surface  having  been  par- 


HATES,    FEATHERS,    AND    SCALES.  21 

tially  worn  down  by  rubbing  against  the  gravel  of  the 
bottom,  or  against  other  objects  in  the  water.  Besides 
the  concentric  lines,  there  are  seen  on  many  of  the  scales, 
especially  those  of  the  lateral  line,  radiating  lines  varying 
in  number  from  one  to  twenty,  or  more,  diverging  from  the 
centre  towards  the  circumference,  and  frequently  con- 
nected by  cross  lines  forming  a  sort  of  net-work  around  the 
centre  (see  c).  Under  the  microscope,  these  lines  appear 
to  be  elevated  ridges,  dividing  the  concentric  lines ;  but  of 
their  use  I  am  ignorant. 

What  I  have  just  stated  is  the  ordinary  explanation  of 
these  fine  concentric  lines ;  but  a  careful  examination  of 
the  structure  with  much  higher  powers  than  we  have  been 
using,  induces  me  to  doubt  its  correctness.  Reverting  to 
the  scales  of  the  Perch, 
let  us  notice  the  clear 
diverging  bands,  which 
look  as  if  the  whole  scale 
had  been  split  in  several 
places,  and  the  openings 
thus  made  filled  with 
uniform  clear  substance. 
The  same  structure  is 
seen  in  many  other 

Scales,  as   in   this  Cycloid  SCALE  OP  FLOTJNDEB. 

one  from  the  Flounder, 

which,  being  coarsely  lined,  shows  the  structure  well ;  or 
in  these  from  the  Green  Wrasse.  I  will  now  apply  to  one 
of  these  a  power  of  600  diameters,  concentrating  the  light 
thrown  through  the  scale  from  the  mirror  by  the  achromatic 
condenser,*  and  examine  the  scale  anew.  You  now  see 
two  distinct  layers ;  the  upper  one  which  bears  the  con- 
centric lines,  and  a  lower  clear  one  which  not  only  fills  the 

*  Called  achromatic,  from  its  being  so  constructed  as  not  to  split  the 
light  coming  through  it  and  cause  colour.  The  term  is  formed  from 
the  Greek  a,  not,  and  x/>«/xa  (chroma),  colour. 


22  EVENINGS   AT    THE    MICROSCOPE. 

radiating  bands,  but  underlies  the  whole  of  the  lined  parts. 
The  concentric  lines  of  the  upper  layer  do  not  now  appear 
to  be  edges  of  successive  plates,  but  irregular  canals  run- 
ning through  the  solid  substance.  This,  however,  is  decep- 
tive :  for,  by  delicate  focussing,  we  perceive  that  each 
portion  marked  by  these  lines  is  really  in  a  different  plane 
from  the  others,  that  the  highest  is  at  the  centre  of  radia- 
tion of  the  scale,  and  that  each  is  successively  lower  till  we 
reach  the  margin.  But  now,  if  with  very  sharp  scissors 
we  cut  one  of  these  scales  longitudinally  through  the 
centre,  and  examine  the  cut  edge,  we  find  that  each  of 
these  lines  forms  a  distinct  ridge.  On  the  other  hand, 
the  under  layer  of  clear  substance  is  quite  smooth,  and 
always  a  little  exceeds  the  margin  of  the  concentrically 
lined  portion.  The  clear  substance  that  fills  the  radiating 
slits  agrees  both  in  texture  and  level  with  this  lower  layer, 
and  is  manifestly  continuous  with  it. 

Hence,  I  think  that,  in  these  slit  scales,  the  upper  layer 
is  formed,  as  commonly  believed,  by  successive  deposits 
from  beneath ;  but  that,  after  a  few  have  been  deposited, 
they  begin  to  slit,  probably  by  contraction  in  becoming 
solid ;  that  the  lower  layer  is  formed  after  each  upper  one 
is  hardened,  exceeding  its  length  by  a  little,  and  filling  up 
the  slit ;  that  this  lower  layer  becomes  the  upper  layer  of 
the  next  course,  slitting,  and  turning  up  its  terminal  edge 
as  it  hardens ;  that  then  the  lower  layer  is  deposited  on 
this,  filling  up  the  slit  as  before  ;  and  that  this  process 
goes  on  as  long  as  the  fish  lives. 

It  is  curious  that,  in  the  scales  of  the  Pike,  the  portions 
thus  separated  by  slitting,  instead  of  expanding  and  leaving 
spaces  to  be  filled  up,  actually  close  over  each  other,  the 
divided  parts  overlapping  considerably,  as  you  may  see  in 
these  specimens.  The  left  hand  scale  (a)  is  from  the 
back ;  the  central  one  (b),  which  has  only  a  deep  narrow 
incision  instead  of  a  tube,  is  from  the  lateral  line ;  and  the 
third  (c)  is  from  the  belly  of  the  fish. 


HAIBS,  FEATHERS,  AND  SCALES.  23 

Let  us  return  now  to  the  scales  of  our  Gold-fish,  and 
examine  a  highly  interesting  structure  connected  with 
them.  The  brilliant  golden  or  silvery  reflection  that  con- 
stitutes the  beauty  of  these  lovely  fishes,  depends  not  on 
the  scales  themselves,  but  on  a  soft  layer  of  pigment  spread 
over  their  inner  surface,  and  seen  through  their  translucent 
substance.  On  carefully  detaching  a  scale,  we  see  on  the 
under  side,  opposite  to  that  portion  only  which  was  ex- 
posed (all  the  concealed  parts  being  colourless),  a  layer  of 
soft  gleaming  substance,  easily  separable,  either  silvery  or 
golden,  according  to  the  hue  of  the  fish.  If  now  we  remove 
a  small  portion  of  this  substance  with  a  fine  needle,  and 


SCALES  OF   PIKE. 


spread  it  on  a  plate  of  thin  glass,  we  shall  find,  by  the  aid 
of  the  microscope,  that  it  consists  of  two  distinct  sub- 
stances ;  the  one  giving  the  colour,  the  other  the  metallic 
lustre.  With  a  power  of  300  diameters,  the  former  is  seen 
to  be  a  layer  of  loose  membranous  cells,  of  an  orange 
colour  in  what  are  properly  called  the  Gold-fishes,  and 
whitish  or  pellucid  in  the  Silver-fishes.  If  we  now  add  a 
minute  drop  of  water  to  the  mass,  and  gently  agitate  it 
with  the  point  of  a  needle,  and  again  submit  it  to  the 
microscope,  we  shall  have  a  beautiful  and  interesting  spec- 
tacle. The  water  around  the  mass  is  seen  to  be  full  of  an 
infinite  number  of  flat  spicula  or  crystals,  varying  much 
in  size,  but  of  very  constant  form,  a  flat  oblong  prism 


24  EVENINGS   AT    THE    MICBOSCOPE. 

with  angular  ends  (as  represented  in  the  accompanying 
engraving).  By  transmitted  light  they  are  so  transparent 
and  filmy  as  to  be  only  just  discernible ; 
but  by  reflected  light,  and  especially 
under  the  sun's  rays,  they  flash  like 
plates  of  polished  steel.  But  what  ap- 
pears most  singular,  is  that  each  spicu- 
lum  is  perpetually  vibrating  and  quiver- 
ing with  a  motion  apparently  quite  spon- 
taneous, but  probably  to  be  referred  to 
slight  vibrations  of  the  water  in  which 
SPICTJLA  OF  GOLD-FISH'S  they  float ;  and  each  independently  of 
the  rest,  so  as  to  convey  the  impres- 
sion to  the  observer  that  each  is  animated  with  life,  though 
the  scale  be  taken  from  a  fish  some  days  dead.  Owing  to 
this  irregular  motion,  and  consequent  change  of  position, 
each  spiculum,  as  it  assumes  or  leaves  the  reflecting  angle, 
is  momentarily  brightening  or  waning,  flashing  out  or 
retiring  into  darkness,  producing  a  magic  effect  on  the 
admiring  observer.  To  this  property,  I  suppose,  is  to  be 
attributed  the  beautiful  pearly  play  of  light  that  marks 
these  lovely  fishes,  as  distinguished  from  the  light  reflected 
by  an  uniformly  polished  surface.  I  have  found  the  pearly 
pigment  of  the  scales  to  be  provided  with  similar  spicula  in 
fishes  widely  differing  in  size,  structure,  and  habits;  as 
the  Gudgeon  and  Minnow,  the  Pike  and  the  Marine  Bream. 
The  spicula  of  these  fishes  agree  in  general  form  with  those 
of  the  Gold-fish  ;  and  also  in  size,  with  the  exception  of 
trifling  variations  in  the  comparative  length  and  breadth. 
The  colouring  matter  is  lodged  in  lengthened  cylindrical 
cells,  arranged  side  by  side,  and  running  across  the  scale ; 
that  is,  in  a  direction  at  right  angles  to  the  lateral  line. 


BLOOD.  25 


CHAPTER  H. 

BLOOD. 

THE  microscope  is  daily  becoming  a  more  and  more  im- 
portant aid  to  legal  investigation.  An  illustration  of  this 
occurred  not  long  ago,  in  which  a  murder  was  brought 
home  to  the  criminal  by  means  of  this  instrument.  Much 
circumstantial  evidence  had  been  adduced  against  him, 
among  which  was  the  fact,  that  a  knife  in  his  possession 
was  smeared  with  blood,  which  had  dried  both  on  the 
blade  and  on  the  handle.  The  prisoner  strove  to  turn 
aside  the  force  of  this  circumstance  by  asserting  that  he 
had  cut  some  raw  beef  with  the  knife,  and  had  omitted  to 
wipe  it. 

The  knife  was  submitted  to  an  eminent  professor  of 
microscopy,  who  immediately  discovered  the  following 
facts  : — 1.  The  stain  was  certainly  blood.  2.  It  was  not 
the  blood  of  a  piece  of  dead  flesh,  but  that  of  a  living  body; 
for  it  had  coagulated  where  it  was  found.  8.  It  was  not 
the  blood  of  an  ox,  sheep,  or  hog.  4.  It  was  human 
blood.  Besides  these  facts,  however,  other  important 
ones  were  revealed  by  the  same  mode  of  investigation. 

5.  Among  the  blood  were  found  some  vegetable  fibres. 

6.  These  were  proved  to  be  cotton  fibres, — agreeing  with 
those   of   the   murdered    man's    shirt    and    neckerchief. 

7.  There  were  present  also  numerous  tesselated  epithelial 
cells.     In  order  to  understand  the  meaning  and  the  bear- 
ing of  this  last  fact,  I  must  explain  that  the  whole  of  the 
internal  surface  of  the  body  is  lined  with  a  delicate  mem- 
brane (a  continuation  of  the  external  skin),  which  dis- 


26  EVENINGS   AT    THE    MICROSCOPE. 

charges  mucus,  and  is  hence  termed  mucus  membrane. 
Now  this  is  composed  of  loose  cells,  which  very  easily 
separate,  called  epithelial  cells  ;  they  are  in  fact  constantly 
in  process  of  being  detached  (in  which  state  they  con- 
stitute the  mucus),, and  of  being  replaced  from  the  tissues 
beneath.  Now  microscopical  anatomists  have  learned 
that  these  epithelial  scales  or  cells,  which  are  so  minute 
as  to  be  un discernible  by  the  unaided  eye,  differ  in  appear- 
ance and  arrangement  in  different  parts  of  the  body. 
Thus,  those  which  line  the  gullet  and  the  lower  part  of 
the  throat  are  tesselated,  or  resemble  the  stones  of  a  pave- 
ment ;  those  that  cover  the  root  of  the  tongue  are  arranged 
in  cylinders  or  tall  cones,  and  are  known  as  columnar; 
while  those  that  line  some  of  the  entrails  carry  little 
waving  hairs  (cilia)  at  their  tips,  and  are  known  as  ciliated 
epithelium. 

The  result  of  the  investigation  left  no  doubt  remaining 
that  with  that  knife  the  throat  of  a  living  human  being, 
which  throat  had  been  protected  by  some  cotton  fabric, 
had  been  cut.  The  accumulation  of  evidence  was  fatal  to 
the  prisoner,  who  without  the  microscopic  testimony  might 
have  escaped. 

But  what  was  there  in  the  dried  brown  stain  that  deter- 
mined it  to  be  blood  ?  And,  particularly,  how  was  it 
proved  to  be  not  the  blood  of  an  ox,  as  the  prisoner 
averred  ?  To  these  points  we  will  now  give  a  moment's 
attention. 

With  this  fine  needle  I  make  a  minute  prick  through 
the  skin  of  my  hand.  A  drop  of  blood  oozes  out,  with 
which  I  smear  this  slip  of  glass.  The  slip  is  now  on  the 
stage  of  the  instrument,  under  a  power  of  600  diameters. 
You  see  an  infinite  number  of  small  roundish  bodies,  of  a 
clear  yellowish  colour,  floating  in  a  colourless  fluid,  but  so 
numerous,  that  it  is  only  here  and  there,  as  near  the 
edges  of  the  smear,  that  you  can  detect  any  interval  in 
their  continuity. 


BLOOD.  27 

These  bodies  are  what  we  frequently  call  the  blood- 
globules,  or,  more  correctly,  blood- disks  ;  since  their  form 
is  not  globular,  but  thin  and  flat,  like  that  of  a  piece  of 
money.  The  slightness  of  their  colour  is  dependent  on 
their  extreme  thinness :  when  a  larger  number  lie  over 
each  other  the  aggregated  colour  is  very  manifest,  as  it 
then  becomes  either  full  dark  red,  or  bright  rich  scarlet ; 
for  to  these  disks  blood  is  entirely  indebted  for  its  well- 
known  hue.  The  blood  of  all  vertebrate  animals  is  com- 
posed principally  of  these  bodies,  which  when  once  seen 
are  easily  recognised  again :  the  microscope  then  readily 
determines  whether  any  given  red  fluid  or  dried  stain  is 
composed  of  blood. 

The  disks  in  the  blood  of  Mammalia,  or  animals  which 
suckle  their  young,  are  circular  or  nearly  so,  and  slightly 
concave  on  both  of  the  surfaces.  On  the  other  hand,  in 
Birds,  Fishes,  and  Reptiles,  their  form  is  elliptical,  and 
the  surfaces  are  flat,  or  slightly  convex.  This  distinction, 
then,  will  at  once  enable  us  to  determine  Mammalian 
blood.*  But  to  determine  the  various  tribes  of  this  great 
class  among  themselves,  we  must  have  recourse  to  another 
criterion, — that  of  dimensions. 

The  blood-disks  of  Man  nearly  agree  in  size  with  those 
of  the  Monkey  tribe,  of  the  Seals  and  Whales,  of  the 
Elephant,  and  of  the  Kangaroo.  Most  other  quadrupeds 
have  them  smaller  than  in  Man ;  the  smallest  of  all  being 
found  in  those  animals  which  chew  the  cud.  The  little 
Musk-deer  of  Java  has  disks  not  more  than  one-fourth  as 
large  as  the  human,  but  these  are  remarkably  minute ;  no 
other  known  animal  approaches  it  in  this  respect :  those  of 
the  Ox  are  about  three -fourths,  and  those  of  the  Sheep 
little  more  than  half  the  human  average. 

Tables  have  been  made  out,  showing  the  comparative 

*  The  Camels  among  Mammalia,  and  the  Lampreys  among  Fishes, 
are  exceptions  to  the  above  rule ;  the  former  having  elliptical  and  con- 
vex blood-disks,  the  latter  circular  and  slightly  concave. 


28 


EVENINGS  AT  THE  MICROSCOPE. 


size  of  these  corpuscles  in  various  animals,  and  such  tables 
are  very  useful;  but  we  must  bear  in  mind  that  the 
average  dimensions  only  are  to  be  looked  for;  since  in 
any  given  quantity  of  blood  under  examination,  we  shall 
not  fail  to  see  that  some  disks  exceed,  while  others  come 
short  of,  the  dimensions  of  the  majority. 

Generally  speaking,  the  blood- disks  in  Birds  and  in 
Fishes  are  about  equal  in  size:  their  form  is,  however, 
that  of  a  more  elongated  ellipse  in  Birds  than  in  Fishes. 
They  may  be  set  down  as  averaging  in  breadth  the  diameter 
of  the  human  disks,  while  their  length  is  about  half  as 
much  again,  or  a  little  more,  in  most  Birds. 


a  Man. 


BLOOD   DISKS. 

Blenny.        c  Frog. 


d  Newt. 


It  is  in  Reptiles  that  we  meet  with  the  largest  disks, 
and  especially  in  those  naked-skinned  species,  the  Frogs 
and  Newts.  A  large  species  inhabiting  the  American 
lakes — Siren  lacertina — has  disks  of  the  extraordinary 
size  of  1 -400th  of  an  inch  long  by  1 -800th  broad,  or  about 
eight  times  as  large  as  those  of  Man,  in  linear  measure. 
Our  common  Newts  afford  us  the  largest  examples  among 
British  animals,  but  they  do  not  reach  above  half  the  size 
just  mentioned. 

Taking  this  drop  of  blood  from  my  finger  as  a  standard 
of  comparison,  we  find,  on  applying  the  micrometer,  that 


BLOOD.  29 

the  disks  run  from  l-2500th  to  l-5000th  of  an  inch ;  but 
that  the  great  majority  are  about  l-3300th  in  diameter. 
On  these  slides  are  samples  of  other  kinds.  This  is  the 
blood  of  a  Fish — the  common  Blenny  or  Shanny  (Blen- 
nius  pholis).  Here  we  see  at  once  the  oval  form  of  the 
disks ;  their  average  is  1 -2800th  by  1 -3300th  of  an  inch. 
Here  is  the  blood  of  a  Frog  (Rana  temporaria) ;  these  are 
more  than  twice  the  size  of  the  fish's ;  for  they  average 
l-1250th  by  l-1800th  of  an  inch.  And,  finally,  I  can 
show  you  a  drop  of  blood  from  this  Smooth-newt  (Lisso- 
triton  punctatus).  The  large  size  of  the  disks  is  now 
plainly  seen,  and  so  indeed  is  the  elegance  of  their  form : 
in  this  case,  as  in  the  last,  we  see  in  each  disk  a  distinct 
roundish  nucleus.  These  run  from  l-703th  to  l-950th  in 
length  by  l-1100th  to  l-1600th  in  breadth;  but  the 
average  are  about  l-800th  by  l-1300th  of  an  inch. 

It  may  interest  you  to  see  these  blood  disks  in  their 
proper  situation,  and  to  observe  the  motion  which  they 
possess  during  the  life  of  their  owners.  It  is,  indeed,  one 
of  the  most  instructive  modes  of  using  this  wonder-work- 
ing instrument  to  look  through  it  at  living  structures,  and 
watch  the  different  processes  of  life  as  they  are  carried  on 
under  our  eyes.  Nor  is  this  at  all  difficult  to  accomplish ; 
for  a  large  number  of  animals  are  so  small  that  we  can 
easily  put  them  upon  the  stage  of  the  microscope ;  and 
are  withal  so  transparent  that  their  coverings  and  various 
tissues  offer  little  or  no  impediment  to  our  discerning  the 
forms  and  movements  of  the  contained  viscera.  And  in 
cases  where  the  entire  animal  is  too  large  to  be  viewed 
under  the  microscope  as  a  whole,  it  sometimes  happens 
that,  by  a  little  contrivance,  we  can  so  secure  the  creature 
as  to  look  without  interruption  on  certain  parts  of  the  body 
which  afford  the  requisite  minuteness  and  transparency. 

I  have  here  a  living  Frog.  You  perceive  that  the  web 
which  connects  the  toes  is  exceedingly  thin  and  trans- 
lucent, yet  arteries  and  veins  meander  through  its  delicate 


30  EVENINGS   AT    THE    MICROSCOPE. 

tissues,  which  are  then  clothed  on  both  surfaces  with  the 
common  skin.  But  you  ask  how  we  can  induce  the  Frog 
to  be  so  polite  as  to  hold  his  paw  up  and  keep  it  steady 
for  our  scientific  investigation.  We  will  manage  that  with- 
out difficulty. 

Most  microscopes  are  furnished  (among  their  accessory 
apparatus)  with  what  is  called  a  frog-plate,  provided  for 
this  very  demonstration.  Here  is  mine.  It  is  a  thin 
plate  of  brass,  two  inches  and  a  half  broad  and  seven  long, 
with  a  number  of  small  holes  pierced  through  it  along 
the  margins,  and  a  large  orifice  near  one  end,  which  is 
covered  with  a  plate  of  glass.  This  is  to  be  Froggy's  bed 
during  the  operation,  for  we  must  make  him  as  comfort- 
able as  circumstances  will  admit. 

Well,  then,  we  take  this  strip  of  linen,  damp  it,  and 
proceed  -to  wrap  up  our  unconscious  subject.  When  we 
have  passed  two  or  three  folds  round  him,  we  bind  a  tape 
round  the  whole,  with  just  sufficient  tightness  to  keep  him 
from  struggling.  One  hind-leg  must  project  from  the 
linen,  and  we  now  pass  a  needle  of  thread  twice  or  thrice 
through  the  drapery  and  round  the  small  of  this  free  leg, 
so  as  to  prevent  him  from  retracting  it. 

Here  then  he  lies,  swathed  like  a  mummy,  with  one 
little  cold  foot  protruded.  Lay  him  carefully  on  the  brass 
plate,  so  that  the  webbed  toes  shall  stretch  across  the 
glass.  Now,  then,  we  pass  another  tape  through  the  mar- 
ginal holes,  and  over  the  body,  to  bind  it  to  the  brass ;  of 
course  taking  care  not  to  cut  the  animal,  but  only  using 
just  as  much  force  as  is  needful  to  prevent  his  wrigglings. 
Now  a  bit  of  thread  round  each  toe,  with  which  we  tie  it 
to  as  many  of  the  holes,  so  as  to  expand  the  web  across 
the  glass.  A  drop  of  cold  water  now  upon  the  swathes  to 
keep  him  cool,  and  a  touch  of  the  same  with  a  feather 
upon  the  toes  to  prevent  them  from  drying  (which  must 
be  repeated  at  intervals  during  the  examination) — and  he 
is  ready. 


BLOOD.  81 

What  a  striking  spectacle  is  now  presented  to  us,  as 
with  a  power  of  300  diameters  we  gaze  on  the  web  of  the 
foot !  There  is  an  area  of  clear  colourless  tissue  filling 
the  field,  marked  all  over  with  delicate  angular  lines,  some- 
thing like  scales ;  this  is  the  tesselated  epithelium  of  the 
surface.  Our  attention  is  caught  by  a  number  of  black 
spots,  often  taking  fantastic  forms,  but  generally  some- 
what star-like ;  these  are  pigment  cells,  on  which  the 
colour  of  the  animal's  skin  is  dependent.  But  the  most 
prominent  feature  is  the  blood.  "Wide  rivers,  with  tor- 
tuous course  roll  across  the  area,  with  many  smaller 
streams  meandering  among  them ;  some  pursuing  an  inde- 
pendent course  below  the  larger,  and  others  branching  out 
of  them,  or  joining  them  at  different  angles.  The  larger 
rivers  are  of  a  deep  orange-red  hue,  the  smaller  faintly 
tinged  with  reddish-yellow.  In  some  of  these  channels 
the  stream  rolls  with  a  majestic  evenness ;  in  others  it 
shoots  along  with  headlong  impetuosity ;  and  in  some  it  is 
almost,  or  even  quite,  stagnant.  By  looking  with  a  steady 
gaze,  we  see  that  in  all  cases  the  stream  is  made  up  of  a 
multitude  of  thin  reddish  disks,  of  exactly  the  same  dimen- 
sions and  appearance  as  those  we  saw  just  now  in  the 
Frog's  blood ;  only  that  here,  being  in  motion,  we  see  very 
distinctly,  as  they  are  rolled  over  each  other,  that  they  are 
disks,  and  not  spherules ;  for  they  forcibly  remind  us  of 
counters,  such  as  are  used  for  play,  supposing  they  were 
made  out  of  pale  red  glass. 

It  is  charming  to  watch  one  of  these  streams  :  selecting 
one  of  medium  size,  where  the  density  is  not  too  great  to 
see  the  individual  disks,  and,  fixing  our  eye  on  the  point 
where  a  branch  issues  from  one  side  of  the  channel,  mark 
the  disks  shoot  by  one  after  another,  some  pursuing  the 
main  course,  and  others  turning  aside  into  the  branch, 
perhaps  so  small  as  to  allow  of  only  a  single  disk  to  pass 
at  once. 

The  streams  do  not  pursue  the  same  uniform  direction. 


32 


EVENINGS   AT    THE    MICKOSCOPE. 


The  larger  ones  do  indeed ;  and  their  course  is  from  the 
extremity  of  the  toes  towards  the  body :  these  are  the 
veins ;  but  the  smaller  streamlets  flow  in  any  direction, 
and  frequently  send  out  side -branches,  which  presently 
return  into  the  stream  from  which  they  issued,  or  unite 
with  others  in  a  very  irregular  net- work.  These  are  the 

capillaries  which  feed 
the  veins,  and  which 
are  themselves  fed  by 
the  arteries,  whose 
course  is  in  the  oppo- 
site direction,  viz., 
from  the  body.  These, 
however,  are  with  dif- 
ficulty seen :  they  are 
more  deeply  seated  in 
the  tissues,  and  are 
less  spread  over  the 
webs,  being  generally 
placed  along  the  bor- 
ders of  the  toes ;  they 
are,  moreover,  fewer 
and  smaller  than  the 
veins  ;  but  the  blood 
in  them  usually  flows  with  more  impetuous  rapidity. 

The  variations  in  the  impetus  of  the  current  which  we 
observe  in  the  same  vessel  are  probably  owing  to  the  men- 
tal emotions  of  the  animal ;  alarm  at  its  unusual  position, 
and  at  the  confinement  which  it  feels  when  it  endeavours 
to  move,  may  suspend  the  action  of  the  heart,  and  thus 
cause  an  interruption  in  the  flow ;  or  analogous  emotions 
may  quicken  the  pulse.  We  will,  however,  now  release 
our  little  prisoner,  who,  though  glad  to  be  at  liberty,  is,  as 
you  see,  none  the  worse  for  his  temporary  imprisonment. 

Let  us  now  look  at  the  circulation  of  the  blood  in  one  of 
the  Invertebrate  Animals.  In  this  thin  glass  cell  of  sea- 


CIHCULATION  IN  FROG'S  FOOT. 


BLOOD. 


water  is  a  small  fragment  of  sea-weed,  and  attached  to  one 
of  its  slender  filaments  you  may  see  three  or  four  tiny 
knobs  of  jelly,  clustered  together  like  a  bunch  of  grapes. 
These  are  animals ;  each  endowed  with  a  distinct  life,  but 
associated  together  by  a  common  stalk,  which  maintains 
the  mutual  vital  connexion  of  the  whole.  It  is  one  of  the 
Social  Tunicata,  and  is  named  Perophora  Listen. 

Though  each  globose  knob  is  no  larger  than  a  small  pin's 
head,  it  is  full  of  organs  which  carry  on  the  various  func- 
tions of  life ;  and,  because  the  whole  tissues  are  as  trans- 
parent as  crystal,  they  allow  us  to  watch  the  processes 
with  perfect  ease.  Take  a  peep  at  it. 

It  is  a  gelatinous  sac,  of  a  form  intermediate  between 
globular  and  cu- 
bical, flattened,  on 
two  opposite  sides, 
with  a  sort  of  wart 
at  the  summit  and 
another  at  the  side, 
each  of  which  is 
pierced  with 
pursed  orifice.  The 
upper  of  these  ori- 
fices admits  water 
for  respiration  and 
food;  the  latter 
passes  through  a 
digestive  system, 
and  is  discharged 
through  the  side 
orifice.  The  di- 
gestive organs  lie  on  that  flattened  side  which  is  farthest 
from  your  eye,  and  are  therefore  dimly  seen. 

The  globose  body  is  inclosed  in  a  coating  of  loose  shape- 
less jelly,  that  passes  off  from  one  of  the  lower  corners 
and  forms  a  short  foot -stalk,  which  unites  with  similar 


PEROPHORA. 


84  EVENINGS   AT    THE    MICROSCOPE. 

foot-stalks  from  the  sister  glojbules,  and  all  together  are 
attached  to  the  sea-weed.  Each  foot-stalk  has  an  organic 
core,  into  which  a  vessel  passes  from  the  body. 

Your  attention  is  first  arrested  by  the  breathing  sac, 
with  its  rows  of  oblong  cells,  all  in  wheel-like  motion.  It 
is  indeed  a  wonderful  object ;  but  for  the  present  neglect 
this,  as  we  will  return  to  it  shortly,  and  direct  your  consi- 
deration to  the  course  of  the  blood. 

It  is  true  the  fluid  which  I  so  name  is  not  red,  like 
that  of  the  Frog  which  you  have  just  been  gazing  at,  nor 
does  it  carry  disks  of  the  same  elegantly  regular  form. 
But  you  have  the  advantage  here  of  tracing,  at  one  view, 
the  whole  course  of  the  circulation,  from  its  first  rush  out 
of  the  heart,  to  its  return  into  that  organ  again. 

At  the  bottom  of  the  interior,  below  the  breathing  sac, 
there  is  an  oblong  cavity,  through  whose  centre  there  runs 
a  long  transparent  vessel,  formed  of  a  delicate  membrane, 
the  appearance  of  which  resembles  that  of  a  long  bag, 
pointed  (but  not  closed)  at  either  end,  and  then  twisted  in 
some  unintelligible  manner,  so  as  to  make  three  turns. 
This  is  the  heart;  and  within  it  are  seen  many  minute 
colourless  globules,  floating  freely  in  a  subtle  fluid  :  this  is 
the  nourishing  juice  of  the  body,  which  we  may,  without 
much  violence,  designate  the  blood.  Now  see  the  circula- 
tion of  this  fluid.  The  membranous  bag  gives  a  spasmodic 
contraction  at  one  end,  and  drives  forward  the  globules 
contained  there ;  the  contraction  in  an  instant  passes  on- 
ward along  the  three  twists  of  the  heart  (the  part  behind 
expanding  immediately  as  the  action  passes  on),  and  the 
globules  are  forcibly  expelled  through  the  narrow  but  open 
extremity.  Meanwhile,  globules  from  around  the  other 
end  have  rushed  in  as  soon  as  that  part  resumed  its  usual 
width,  which  in  turn  are  driven  forward  by  a  periodic  repe- 
tition of  the  contraction  and  expansion  of  the  heart. 

The  globules  thus  periodically  driven  forth  from  the 
heart,  now  let  us  watch,  and  see  what  becomes  of  them. 


BLOOD.  85 

They  do  not  appear  to  pass  into  any  denned  system  of 
vessels,  that  we  may  call  arteries,  but  to  find  their  way 
through  the  interstices  of  the  various  organs  in  the  general 
cavity  of  the  body. 

The  greater  number  of  globules  pass  immediately  from 
the  heart  through  a  vessel  into  the  short  foot- stalk,  where 
they  accumulate  in  a  large  reservoir ;  but  the  rest  pass  up 
along  the  side  of  the  body,  which  (in  the  aspect  in  which 
we  are  looking  at  it)  is  the  right.  As  they  proceed  (by 
jerks,  of  course,  impelled  by  the  contractions  of  the  heart), 
some  find  their  way  into  the  space  between  the  breathing 
surfaces,  through  narrow  slits  along  the  edges  of  the  sac, 
and  wind  along  between  the  oval  ciliary  wheels,  which  we 
will  presently  consider.  Besides  these,  however,  other 
globules  wind  along  between  the  outer  surfaces  of  the  sac 
and  the  inner  surface  of  the  body-walls. 

But  to  return  to  the  current  which  passes  up  the  right 
side :  arriving  at  the  upper  angle  of  the  body,  the  stream 
turns  off  to  the  left  abruptly,  principally  passing  along  a 
fold  or  groove  in  the  exterior  of  the  breathing  sac  until  it 
reaches  the  left  side,  down  which  it  passes,  and  along  the 
bottom,  until  it  arrives  at  the  entrance  of  the  heart,  and 
rushes  in  to  fill  the  vacuum  produced  by  the  expansion  of 
its  walls  after  the  periodic  contraction.  This  is  the  perfect 
circle ;  but  the  minor  streams  that  had  forked  off  sideways 
in  the  course,  as  those  within  the  sac  for  example,  find 
their  way  to  the  entrance  of  the  heart  by  shorter  and  more 
irregular  courses. 

One  or  two  things  connected  with  this  circulatory  system 
are  worthy  of  special  notice.  The  first  is,  that  its  direc- 
tion is  not  constant,  but  reversible.  After  we  have  watched 
this  course  followed  with  regularity  for  perhaps  a  hundred 
pulsations  or  so,  all  of  a  sudden  the  heart  ceases  to  beat, 
and  all  the  globules  rest  in  their  circling  course,  that  we 
had  supposed  incessant.  Strange  to  behold,  after  a  pause 
of  two  or  three  seconds,  the  pulsation  begins  again,  but  at 

D2 


86  EVENINGS    AT    THE    MICROSCOPE. 

the  opposite  end  of  the  heart,  and  proceeds  with  perfect 
regularity,  just  as  before,  but  in  the  opposite  direction. 
The  globules,  of  course,  obey  the  new  impulse,  enter  at 
their  former  exit,  and  pass  out  at  their  former  entrance, 
and  perform  their  circulation  in  every  respect  the  same  as 
before,  but  in  the  reverse  direction. 

Those  globules  that  pass  through  the  vessel  into  the 
foot-stalk  appear  to  accumulate  there  as  in  a  reservoir, 
until  the  course  is  changed,  when  they  crowd  into  the 
heart  again,  and  perform  their  grand  tour.  Yet  there  is  a 
measure  of  circulation  here,  for  even  in  the  connecting 
vessel  one  stream  ascends  from  the  reservoir  into  the  body, 
as  the  other  (and  principal  one)  descends  into  it  from  the 
heart ;  and  so,  vice  versa. 

I  have  spoken  of  these  motions  as  being  performed  with 
regularity ;  but  if  you  look  closely,  you  will  see  that  this 
must  be  understood  with  some  qualification.  The  pulsa- 
tions are  not  quite  uniform,  being  sometimes  more  languid, 
sometimes  more  vigorous  ;  perhaps  forty  beats  in  a  minute 
may  be  the  average ;  but  I  have  counted  sixty,  and,  pre- 
sently after,  thirty ;  I  have  counted  twenty  beats  in  one 
half-minute,  and  only  fifteen  in  the  next.  The  period 
during  which  one  course  continues  is  equally  uncertain ; 
but  about  two  minutes  may  be  the  usual  time.  Sometimes 
the  pulsation  intermits  for  a  second  or  so,  and  then  goes 
on  in  the  same  direction ;  and  sometimes  there  is  a  curious 
variation  in  the  heart's  action,— a  faint  and  then  a  strong 
beat,  a  faint  and  a  strong  one,  and  so  alternately  for  some 
time. 

The  phenomena  of  respiration  are  so  closely  connected 
with  those  of  circulation  that  it  is  not  at  all  out  of  the  way 
to  turn  from  the  latter  to  the  former ;  not  to  say  that  it 
would  be  high  treason  against  scientific  curiosity  if  I  were 
to  remove  this  object  without  explaining  to  you  that  mar- 
vellous play  of  wheels  that  occupies  the  largest  part  of  the 
area  that  you  behold.  As  you  look  on  the  globe,  you  ob- 


BLOOD.  37 

serve,  hanging  down  from  the  upper  extremity,  and  reaching 
nearly  to  the  bottom  in  one  direction  and  almost  from  side 
to  side  in  another,  a  transparent  square  veil,  which  is 
indeed  a  flat  membranous  bag,  having  its  sides  pretty  close 
together,  with  small  openings  along  its  edges,  and  an 
orifice  at  the  bottom  leading  into  the  stomach. 

The  mouth  of  this  sac  is  in  close  connexion  with  the 
upper  or  principal  orifice,  and  therefore  receives  the  water, 
which  is  constantly  flowing  in,  while  that  aperture  is  ex- 
panded. This  fluid  then  bathes  the  whole  interior  of  the 
sac ;  but  a  portion  of  it  escapes  by  the  lateral  openings 
into  the  cavity  of  the  body,  between  the  sac  and  the 
mantle,  and  is  discharged  through  the  secondary,  or  side 
orifice. 

The  inner  surface  of  this  transparent  sac  is  studded 
with  rings  of  a  long  oval  figure,  set  side  by  side  in  four 
rows.  These  rings  appear  to  consist  of  a  slight  elevation 
of  the  general  membranous  surface,  so  as  to  make  little 
shallow  cells,  the  whole  edges  of  which  are  fringed  with 
cilia,  whose  movements  make  waves,  that  follow  each 
other  round  the  course  in  regular  succession.  In  truth  it 
is  a  beautiful  sight  to  see  forty  or  more  of  these  rings,  all 
set  round  their  interior  with  what  look  like  the  cogs  on  a 
watch  wheel,  dark  and  distinct,  running  round  and  round 
with  an  even,  moderately  rapid,  ceaseless  motion.  These 
black  running  figures,  so  like  cogs  and  so  well  defined  as 
they  are,  are  merely  an  optical  delusion;  they  do  not 
represent  the  cilia,  but  merely  the  waves  which  the  cilia 
make :  the  cilia  themselves  are  exceedingly  slender  close- 
set  hairs,  as  may  be  seen  at  the  ends  of  the  ovals,  where  a 
slight  alteration  of  position  prevents  the  waves  from  taking 
the  tooth-like  appearance.  Sometimes  one  here  and  there 
of  the  ovals  ceases  to  play,  while  the  rest  continue ;  and, 
now  and  then,  the  whole  are  suddenly  arrested  simultane- 
ously, as  if  by  magic,  and  presently  all  start  together  again, 
which  has  a  most  charming  effect.  A  still  more  singular 


38  EVENINGS   AT    THE    MICROSCOPE. 

circumstance  is,  that  while  in  general  the  ciliary  wave  runs 
in  the  same  direction  in  the  different  ovals,  there  will  he 
one  here  and  there  in  which  the  course  is  reversed ;  and  I 
think  that  the  animal  has  the  power  of  choosing  the  direc- 
tion of  the  waves,  of  setting  them  going  and  of  stopping 
them,  individually  as  well  as  collectively. 

The  object  of  these  ciliary  wheels  is  to  keep  up  a  con- 
stant current  in  the  water.  This  fluid,  as  I  have  said, 
enters  from  without,  through  the  upper  orifice  of  the  body, 
and  is  hurled  over  the  whole  surface  of  the  breathing  sac 
by  means  of  the  ciliary  waves,  parting  with  its  oxygen,  as 
it  goes,  to  the  blood,  which  streams,  as  we  saw,  every- 
where between  the  rows  of  wheels.  But  the  water  has 
another  function :  it  carries  particles  of  organic  matter 
with  it,  which  are  suitable  for  the  nourishment  of  the 
creature;  these  atoms  are  carried  by  the  currents  to  the 
bottom  of  the  sac,  and  are  poured  into  the  stomach,  where 
they  are  digested ;  the  remains,  together  with  the  waste 
water,  being  discharged  through  the  lateral  orifice. 

Thus  we  see  how  closely  connected  are  the  three  great 
processes  of  circulation,  respiration,  and  digestion. 


MOLLUSCA.  89 


CHAPTER  m. 
MOLLUSCA:  THEIR  SHELLS,  TONGUES,  EYES,  AND  EARS. 

ONE  of  the  most  interesting  aspects  of  microscopic  study 
is  that  in  which  it  reveals  the  intimate  structure  of  objects, 
which,  to  the  unassisted  eye,  appear  simple  or  nearly  so, 
but  which  prove  by  the  aid  of  magnifying  power  to  be 
complex.  Thus  we  are  often  introduced  to  very  curious 
contrivances  (if  I  may  use  such  a  word  in  reference  to  the 
works  of  God),  by  which  difficulties  are  overcome,  and 
substances,  which  would  seem  at  first  wholly  unfit  for 
certain  duties,  are  in  the  most  admirable  manner  adapted 
to  fulfil  them. 

The  combination  of  strength  and  lightness  is  always  a 
difficult  problem  in  human  art;  its  successful  solution 
always  excites  our  admiration.  In  the  Divine  mechanics, 
too,  it  is  very  often  required,  and  the  variety  of  modes  in 
which  it  is  accomplished  are  in  the  highest  degree  novel 
and  suggestive.  We  lately  saw  one  of  these  in  the  struc- 
ture of  a  feather,  in  the  contrivance  by  which  extreme 
lightness  of  material  was  made,  by  a  most  remarkable 
arrangement,  to  ofier  a  firm  resistance  to  opposing  force. 
I  have  now  another  example  to  show  you,  in  which  a 
material,  in  itself  heavy,  is  by  its  arrangement  made  very 
light,  while  it  preserves  its  strength. 

You  have  seen  many  times,  when  walking  along  the 
yellow  sands  kissed  by  the  rippling  waves,  the  shell,  or 
bone,  as  it  is  sometimes  called,  of  the  Cuttle-fish.  You 
know  that  it  consists  of  a  shallow  boat-shaped  shell,  the 
hollow  of  which  is  filled  with  a  white  substance,  which  can 


40  EVENINGS   AT    THE    MICROSCOPE. 

be  scraped  away  even  with  the  finger-nail,  and  which 
is  sometimes  used  as  pounce,  to  rub  on  paper  from  which 
writing  has  been  erased.  It  is  this  substance  of  which  I 
mean  now  to  speak. 

The  possessor  of  this  structure  is  a  member  of  the 
numerous  class  MOLLUSCA,*  which  are  generally  charac- 
terised by  being  inclosed  in  shells.  Now  shell,  as  we 
all  know,  is  a  solid,  stony  substance,  much  heavier  than 
water;  take  into  your  hand  that  large  Cassis  on  the 
mantel-piece,  and  observe  its  great  weight  and  compact- 
ness. It  is,  in  fact,  real  limestone ;  differing  from  that  of 
the  rocks  only  in  this,  that  it  has  been  deposited  by  the 
living  organic  cells  of  an  animal,  and  arranged  in  a  de- 
finite form.  We  will  presently  examine  other  examples. 
The  "cuttle-bone"  is  a  shell,  not  indeed  inclosing  the 
animal,  but  inclosed  by  it,  being  contained  within  a 
cavity  in  the  substance  of  the  fleshy  mantle ;  cut  open  the 
mantle,  and  the  shell  instantly  drops  out. 

The  Cuttle  is  a  rapid  swimmer  through  the  open  sea. 
A  shell  so  large  as  this,  if  solid  and  compact  like  that  of 
the  Cassis,  would  condemn  it  to  grovel  on  the  bottom,  and 
frustrate  all  the  instincts  of  its  nature.  On  the  other 
hand,  it  needs  the  strength  and  support  of  a  solid  column. 
Wonderful  to  tell,  the  calcareous  f  shell  is  made  not  only  to 
be  no  hindrance  to  its  swimming,  but  to  contribute  greatly 
to  its  buoyancy :  it  is  what  the  string  of  corks  is  to  the 
bather  who  cannot  swim,  it  is  a  float.  Throw  this  entire 
cuttle-shell  into  water ;  it  floats  on  the  surface  as  buoy- 
antly as  if  it  were  actually  carved  out  of  cork. 

I  cut  with  a  keen  knife  a  little  cube  out  of  the  shell, 
and,  fixing  it  on  the  end  of  the  revolving  stage-needle, 
apply  a  low  power,  say  seventy  diameters,  using  reflected 

*  From  the  Latin  mollis,  soft;  a  name  given  by  Cuvier  to  this 
class  from  their  bodies  being  always  soft,  whether  bearing  shells  or 
not. 

f  From  calx,  Latin  for  lime. 


MOLLUSCA :    THEIB    SHELLS. 


41 


light.  We  are  looking  now  at  the  perpendicular  section  ; 
is  it  not  a  beautiful  object  ?  you  might  fancy  yourself 
looking  at  one  of  the  noble  icebergs  that  majestically 
navigate  the  polar  seas,  when  it  is  rendered  porous  and 
laminated  by  the  rains  of  spring.  You  see  a  number  of 
thin  horizontal  tiers 
or  stages,  perfectly 
parallel  and  equi-dis- 
tant,  about  one-for- 
tieth of  an  inch  apart, 
rising  above  each 
other  like  the  floors 
of  an  edifice.  These 
are  connected  together 
by  an  infinite  multi- 
tude of  thin  pillars 

Of   crystal,    Or    rather  CUTTLE-SHELL. 

leaves,  some  of  which          °  PerP€ndicQlar-      6  Horizontal, 
show  their  edges  towards  us,  others  their  broader  sides, 
and  others  are  broken  off  at  various  distances,  the  frag- 
ments standing  up  from  the  floor,  or  depending  from  the 
roof,  like  stalactites  and  stalagmites  in  a  cavern.* 

This  whole  series  of  crystal  floors  and  supporting  plates 
is  formed  of  calcareous  matter, — limestone,  in  short ;  but 
though  the  latter  are  set  in  such  close  array  that  the  eye 
cannot  penetrate  to  any  appreciable  distance  between 
them,  their  extreme  thinness  renders  the  whole  structure 
very  light,  the  interstices  being  occupied  by  air. 

But  now  if  I  give  the  stage-needle  half  a  revolution,  we 
shall  have  the  horizontal  section  presented  to  the  eye.  In 
this  aspect  we  acquire  much  more  information  as  to  the 
structure.  The  cut  has  been  made  very  close  to  one  of 

*  In  calcareous  districts  the  water  trickling  through  into  caverns 
often  forms  shapeless  masses  on  the  floor  or  hanging  like  icicles  from 
the  roof ;  in  the  former  case  they  are  called  stalagmites,  in  the  latter 
stalactites. 


42  EVENINGS   AT    THE    MICROSCOPE. 

the  horizontal  floors,  which  we  see  marked  all  over  with 
a  great  number  of  lines,  each  of  which  runs  hither  and 
thither,  in  a  very  sinuous  pattern.  The  lines  are  made  up 
of  a  brilliant  sparkling  substance;  they  are,  in  fact,  the 
basal  portions  of  what  we  saw  in  the  other  section  as  thin 
perpendicular  plates ;  I  have  cut  off  the  plates  close  to 
the  bottom,  and  what  we  see  is  their  insertion  into  the 
floor. 

Thus  we  perceive  that  what  we  took  for  a  multitude  of 
plates,  were  but  the  various  doublings  and  infoldings  of  a 
single  plate  of  great  length,  running  quite  across  the 
floor :  an  arrangement  by  which  the  strength  of  the  ma- 
terial is  greatly  augmented.  You  have  often  seen  the 
mode  in  which  light  walls  are  made  of  corrugated  iron, 
especially  at  railway  stations  ;  and  are  doubtless  aware  that 
the  corrugation,  or  bending  in  or  out,  imparts  a  strength 
to  it  which  the  mere  sheet  iron,  if  set  up  as  a  smooth, 
plane  surface,  would  in  no  wise  possess.  The  principle  is 
exactly  the  same  in  the  two  cases ;  but  the  corrugation  of 
the  limestone  plates  in  the  cuttle -shell  is  far  more  perfect 
than  that  of  the  iron ;  added  to  which  there  is  the  other 
advantage,  that  the  aggregate  mass  of  material  is  made 
highly  buoyant  by  the  large  bulk  of  empty  space  that 
intervenes  between  the  sinuous  folds  of  the  crystal  plates. 

It  may  be  interesting  to  compare  with  this  the  structure 
of  the  more  solid  shells  of  bivalves,  which  have  been  so 
elaborately  studied  by  Dr.  Carpenter.  In  general,  these 
consist  of  two  very  distinct  layers,  well  seen  in  the  valve 
of  the  Pearl  Oyster  and  its  allies.  The  Pinna,  or  Wing- 
shell,  the  largest  of  our  native  bivalves,  affords  us  a  good 
example,  especially  of  the  external  layer,  since  here  this 
layer  projects  beyond  the  inner  one,  in  thin  transparent 
edges,  which  gives  us  an  opportunity  of  examining  their 
structure  without  any  artificial  preparation.  This  frag- 
ment, taken  from  the  edge  of  one  of  those  leafy  expan- 
sions, we  will  examine  with  a  low  magnifying  power.  Each 


MOLLUSCA:  THEIR  SHELLS. 


43 


of  its  surfaces  has  a  sort  of  facetted,  or  honeycombed 
appearance ;  and  the  broken  edges,  which  even  to  the 
naked  eye  appear  fibrous,  are  seen  to  resemble  a  number 
of  basaltic  columns.  "  The  shell  is  thus  seen  to  be  com- 
posed of  a  vast  number  of  prisms,  having  a  tolerably 
uniform  size,  and  usually  presenting  an  approach  to  the 
hexagonal  shape.  These  are  arranged  perpendicularly,  or 
nearly  so,  to  the  surface  of  the  lamina  of  the  shell ;  so 
that  its  thickness  is  formed  by  their  length,  and  its  two 
surfaces  by  their  extremities."* 


SECTION   OF   NACRE   FROM   PEARL   OYSTI 


The  inner  layer  of  such  shells  is  remarkable  for  pos- 
sessing in  different  degrees  the  property  of  reflecting  rain- 
bow-like colours,  often  with  great  delicacy  and  splendour ; 
and  this  is  termed  nacre,  or  familiarly  "  mother-of-pearl." 
This  iridescent  lustre  depends,  as  Sir  David  Brewster  has 
shown,!  upon  a  multitude  of  grooves  or  fine  lines,  which 
run  in  a  very  waved  pattern,  but  nearly  parallel  to  each 
other,  across  the  surface  of  the  nacre.  "As  these  lines 
are  not  obliterated  by  any  amount  of  polishing,  it  is 

*  Carpenter,  "  The  Microscope,"  590.  f  "  K^  Trans.,"  1814. 


44  EVENINGS    AT    THE    MICEOSCOPE. 

obvious  that  their  presence  depends  upon  something  pe- 
culiar in  the  texture  of  this  substance,  and  not  upon  any 
mere  superficial  arrangement.  When  a  piece  of  nacre  is 
carefully  examined,  it  becomes  evident  that  the  lines  are 
produced  by  the  cropping  out  of  laminae  of  shell,  situated 
more  or  less  obliquely  to  the  plane  of  the  surface.  The 
greater  the  dip  of  these  laminae,  the  closer  will  their  edges 
be ;  whilst  the  less  the  angle  which  they  make  with  the 
surface,  the  wider  will  be  the  interval  between  the  lines. 
When  the  section  passes  for  any  distance  in  the  plane  of 
a  lamina,  no  lines  will  present  themselves  on  that  space. 
And  thus  the  appearance  of  a  section  of  nacre  is  such, 
as  to  have  been  aptly  compared  by  Sir  J.  Herschel  to  the 
surface  of  a  smoothed  deal  board,  in  which  the  woody 
layers  are  cut  perpendicularly  to  their  surface  in  one  part, 
and  nearly  in  their  plane  in  another."* 

Those  beautiful  objects, — so  much  prized  for  personal 
adornment, — pearls,  are  concretions  accidentally  formed 
within  the  shells  of  such  mollusks,  and  are  wholly  com- 
posed of  the  inner  layer.  Drs.  Kelaart  and  Mobius  have 
recently  published  some  highly  interesting  observations  on 
the  causes  both  of  the  iridescence  and  of  the  pearly 
lustre ;  and  these  I  will  cite  from  the  abstract  translation 
of  them  made  by  Mr.  Dallas. 

"  The  surface  of  pearls  is  not  perfectly  smooth,  but 
covered  with  very  fine  microscopic  elevations  and  depres- 
sions. These  are  more  or  less  irregular  in  their  altitude, 
but  approach  most  nearly  to  equality  in  pearls  of  the 
finest  water.  In  pearls  which  exhibit  a  certain  iridescence, 
and  which,  when  turned  in  different  directions  towards  the 
eye,  present  even  very  faint  bluish,  greenish,  and  reddish 
tints,  the  surface  is  found  to  present  delicate  irregular 
curved  furrows,  which  either  run  tolerably  parallel  to  each 
other,  or  form  small  irregular  closed  curves.  This  is  due 
to  the  mode  of  growth  of  the  pearl,  in  which  thin  layers 
*  Carpenter,  "  The  Microscope  "  5<>A 


MOLLUSCA:  THEIR  SHELLS.  45 

of  nacre,  of  small  dimensions,  have  been  laid  over  each 
other.  There  is  no  continuous  layer  over  the  pearl,  but  a 
number  of  small  portions  which  sometimes  overlie  the 
margins  of  the  subjacent  layers,  and  sometimes  leave 
them  uncovered.  This  structure  is  seen  most  distinctly 
in  the  pearl  shell,  where  the  conditions  are  rendered  more 
simple  by  the  layers  being  deposited  on  a  flat,  or  but 
slightly  curved  surface.  The  distance  of  the  furrows  from 
each  other  is  not  always  the  same ;  sometimes  they  may 
be  recognised  with  the  simple  lens,  while  on  other  parts 
they  approach  within  gVoi^h  °f  an  mc^  °f  eac^  other. 
That  the  iridescence  of  nacre,  or  the  nacreous  colour,  as 
distinguished  from  pearly  lustre,  is  caused  by  the  inter- 
ference of  the  light  reflected  from  these  furrows  and  the 
intervening  edges  of  the  strata,  is  proved  by  the  circum- 
stance, ascertained  by  Brewster,  that  impressions  of 
mother-of-pearl  taken  in  red  or  black  sealing-wax  exhibit 
the  same  phenomena  of  colour  distinctly.  In  pearls,  in 
consequence  of  their  spherical  form,  the  different  masses 
of  coloured  light  are  so  diffused  that  they  unite  to  form 
white  light ;  and  this  takes  place  with  the  greater  perfec- 
tion in  proportion  as  the  furrows  are  lost,  and  become 
converted  into  a  surface  of  fine  elevations  and  depres- 
sions. 

"  For  their  lustre,  pearls  are  indebted  to  their  being 
composed  of  fine  layers,  which  allow  light  to  pass  through 
them ;  whilst  the  numerous  layers,  lying  one  under  the 
other,  disperse  and  reflect  the  light  in  such  a  manner  that 
it  returns  and  mixes  with  that  which  is  directly  thrown 
back  from  the  outer  surface.  It  is  the  co-operation  of 
light  reflected  from  the  surface,  with  light  dispersed  and 
reflected  in  the  interior,  that  gives  rise  to  lustre  ;  for  this 
reason  the  knots  of  window-glass  exhibit  pearly  lustre,  and 
the  membranes  of  pearls  deprived  of  their  line  are  almost 
as  lustrous  as  solid  pearls,  except  that  their  whiteness  is 
destroyed.  «  The  two  masses  of  light  entering  the  eye,  act 


46  EVENINGS   AT    THE    MICROSCOPE. 

upon  it  from  different  distances.  Now,  as  it  adapts  itself 
to  the  body  seen  through  the  transparent  layer,  it  cannot 
distinctly  see  the  light  reflected  from  the  surface,  and 
the  consciousness  of  this  infinitely  perceptible  reflection 
produces  the  phenomena  of  lustre.'  *  The  thinner  and 
the  more  transparent  the  layers  of  which  the  pearl 
consists,  the  more  beautiful  is  its  lustre ;  and  in  this 
respect  the  sea-pearls  excel  those  of  our  river-mol- 
lusks."  f 

We  will  pass  now,  by  an  easy  transition,  from  the  shells 
of  the  Mollusca  to  their  tongues.  Who  that  looks  at  the 
weather-worn  cone  of  the  Limpet,  as  he  adheres  sluggishly 
to  the  rock  between  tide-levels,  would  suspect  that  he 
carries  coiled  up  in  his  throat  a  tongue  twice  as  long 
as  his  shell  ?  And  that  this  tongue  is  armed  with  thou- 
sands of  crystal  teeth,  all  arranged  with  the  most  consum- 
mate art  in  a  pattern  of  perfect  regularity  ?  It  sounds 
almost  like  a  fable  to  be  told  that  the  great  Spotted  Slug, 
which  we  sometimes  find  crawling  in  damp  cellars,  carries 
a  tongue  armed  with  26,800  teeth !  Yet  there  is  no  doubt 
of  the  fact. 

You  see  on  this  slip  of  glass  a  very  slender  band  about 
two  inches  in  length.  This  is  the  tongue  of  the  common 
Periwinkle.  While  it  was  in  the  living  animal,  its  fore -part 
occupied  the  floor  of  the  mouth,  whence  it  passed  down 
below  the  throat,  and,  turning  towards  the  right  side, 
formed  a  close  spire  of  many  whorls,  exactly  like  a  coil  of 
rope,  which  rested  on  the  gullet.  Here  we  have  it  ex- 
tracted, uncoiled,  cleansed,  and  affixed  to  a  slip  of  glass 
for  microscopical  examination. 

Only  a  small  portion  of  the  band  is  visible  at  a  time 
with  such  a  power  as  is  necessary  to  display  the  structure  ; 
but  by  means  of  the  stage-movement  we  can  bring  the 
whole  in  succession  under  the  eye,  and  discover  that,  with 
some  modifications  of  form,  the  same  essential  plan  of 

*  Dove,  "  Farbenlehre,"  117.       f  "  Ann.  &  Mag.  N.H."  j  Feb.  1858. 


MOLLUSCA:  THEIR  TONGUES.  47 

structure,  and  even  the  same  elements,  exist  throughout. 
Concentrating  our  attention  on  a  single  transverse  series 
of  the  numerous  curved  lines  that  at  first  sight  bewilder  the 
mind,  we  perceive,  by  delicate  focussing,  that  the  object 
before  us  consists  of  a  number  of  hooks  projecting  from 
the  surface  of  the  translucent  band,  and  arching  downward. 
In  this  case  a  single  row  consists  of  seven  such  hooked 
plates  or  teeth ;  one  in  the  centre  and  three  on  each  side. 
Each  hooked  plate  has  its  arching  tip  cut  into  five  tooth- 
lets,  of  which  the  central  one  is  the  largest ;  and  its  base 
is  united  with  the  cartilaginous  or  gristly  substance  of  the 
band.  Only  the  middle  plate  is  symmetrical ;  the  lateral 
ones  bend  inwards  towards  the  central  one,  and  are  sym- 
metrical only  when  considered  in  pairs,  each  associated 
with  its  opposite.  The  plates  are  perfectly  transparent, 
but  of  a  yellow  horny  colour ;  they  are  very  hard ;  and,  as 
they  are  not  dissolved  by  acids,  it  has  been  supposed  that 
their  substance  is  siliceous  (having  the  nature  of  flint) ; 
but  they  are  more  probably  chitinous,  or  formed  of  the 
substance  of  which  the  hard  parts  of  insects  are  com- 
posed. The  tongue  before  us  has  600  rows  such  as  these, 
each,  as  we  see,  closely  following,  and  indeed  overlapping, 
its  predecessor ;  so  that  we  can  never  look  at  a  single  row 
without  at  the  same  time  seeing  others  which  it  overlaps, 
or  by  which  it  is  overlapped. 

The  specimen  which  I  will  now  show  you  is  broader,  but 
shorter.  It  is  the  tongue  of  Trochus  ziziphinus,  a  large 
and  handsome  shell  of  regularly  conical  form,  not  un- 
common on  our  rocky  shores.  It  is  perhaps  a  more 
interesting  study  than  that  of  the  Periwinkle.  There  are 
here,  you  observe,  three  constituent  elements  in  the  pat- 
tern. First,  a  delicate  glassy  central  tooth,  tapering  to  a 
fine  point,  and  cut  into  minute  saw-teeth  along  each  edge. 
Then  a  series,  of  five  on  each  side,  of  similar  glassy 
pointed  leaves,  bending  inward ;  and  outside  these,  on 
either  hand,  are  a  great  number  of  stout  dark-coloured 


48  EVENINGS    AT    THE    MICROSCOPE. 

hooks,  arching  forward  and  inward,  each  notched  with  saw- 
teeth, and  diminishing  in  thickness  as  they  recede  from 
the  centre. 

The  manner  of  using  this  elaborate  organ  is  no  less 
curious  than  is  its  structure.  During  life  it  is  only  the 
front  portion — not  more  than  one-third — of  the  band  that 
is  in  use ;  this  is  spread  out  on  the  floor  of  the  mouth, 
with  the  teeth  projecting  and  hooking  backwards.  The 
remainder  has  its  edges  rolled  over  towards  each  other, 
forming  a  tube  closed  at  its  extremity,  which,  as  I  have 


TONGUE   OF   TROCHUS. 


already  observed,   is   coiled   away  (in   the   long-tongued 
kinds)  among  the  viscera. 

The  mode  in  which  the  tongue  is  used  may  be  readily 
seen  by  watching  the  actions  of  a  Periwinkle  in  a  marine, 
or  a  Pond-snail  in  a  fresh-water  aquarium.  When  the 
conferva  has  begun  to  form  a  thin  green  growth  on  the 
glass  sides  of  the  tank,  the  Mollusca  are  incessantly  en- 
gaged in  feeding  on  it,  and  rasping  it  away  with  this  toothed 
band.  "  The  upper  lip  with  its  mandible  is  raised ;  the 
lower  lip  expands ;  the  tongue  is  protruded,  and  applied  to 


MOLLUSCA  I  THEIR  TONGUES.  49 

the  surface  for  an  instant,  and  then  withdrawn ;  its  teeth 
glitter  like  glass-paper,  and  in  the  Pond-snail  it  is  so 
flexible  that  frequently  it  will  catch  against  projecting 
points,  and  be  drawn  out  of  shape  slightly  as  it  vibrates 
over  the  surface."* 

Perhaps  every  variety  is  accompanied  by  some  variation 
in  food  or  manner  of  feeding.  With  the  Trochus,  the 
proboscis,  a  tube  with  thick  fleshy  walls,  is  rapidly  turned 
inside  out  to  a  certain  extent,  until  a  surface  is  brought 
into  contact  with  the  glass,  having  a  silky  lustre  :  this  is 
the  tongue ;  it  is  moved  with  a  short  sweep,  and  then  the 
tubular  proboscis  infolds  its  walls  again ;  the  tongue  dis- 
appearing, and  every  filament  of  conferva  being  carried  up 
into  the  interior  from  the  little  area  which  had  been  swept. 
The  next  instant,  the  foot  meanwhile  having  made  a  small 
advance,  the  proboscis  unfolds  again,  the  tongue  makes 
another  sweep,  and  again  the  whole  is  withdrawn ;  and 
this  proceeds  with  great  regularity.  I  can  compare  the 
action  to  nothing  so  well  as  to  the  manner  in  which  the 
tongue  of  an  ox  licks  up  the  grass  of  the  field,  or  to  the 
action  of  a  mower  cutting  down  swathe  after,  swathe  as  he 
marches  along.  The  latter  comparison  is  more  striking,  on 
account  of  the  marks  of  progress  which  each  operator  leaves 
behind  him.  Though  the  confervoid  plants  are  swept  off 
by  the  tongue  of  the  Mollusk,  it  is  not  done  so  cleanly  but 
that  a  mark  is  left  where  they  grew;  and  the  peculiar 
form  and  structure  of  the  tongue,  which  I  have  above 
noticed,  leave  a  series  of  successive  curves  all  along  the 
course  which  the  Mollusk  has  followed,  very  closely  like 
those  which  mark  the  individual  swathes  cut  by  the  mower 
in  his  course  through  the  field. 

The  Periwinkle's  table-manners  differ  slightly  from  those 

of  his  relations.     When  he  eats,  he  separates  two  little 

fleshy  lips,  and  the  glistening,  glass-like  tongue  is  seen, 

or  rather  the  rounded  extremity  of  a  bend  of  it,  rapidly 

*  Woodward's  "  Mollusca,"  161. 


50  EVENINGS   AT    THE    MICROSCOPE. 

running  round  like  an  endless  band  in  some  piece  of 
machinery ;  only  that  the  tooth  points,  as  they  run  by, 
remind  one  rather  of  a  watch- wheel.  For  an  instant  this 
appears,  then  the  lips  close  again,  and  presently  re-open, 
and  the  tongue  again  performs  its  rasping.  It  is  wonder- 
ful to  see ; — perhaps  not  more  wonderful  than  any  other 
of  God's  great  works,  never  more  great  than  when 
minutely  great ;  but  the  action  and  the  instrument,  the 
perfect  way  in  which  it  works,  and  the  effectiveness  with 
which  the  vegetation  is  cleared  away  before  it,  all  strike 
the  mind  with  more  than  usual  force,  as  exhibitions  of  the 
skill  of  the  Creator. 

As  the  Periwinkle  moves  along,  mowing  his  sea-grass  as 
he  goes,  he  carries  before  him  two  soft  and  flexible  horns, 
marked  with  zebra-like  bands  of  black  and  white,  which 
he  constantly  waves  about.  These  are  organs  of  some 
sense,  probably  of  touch,  and  are  therefore  called  tentacles 
(or  tryers) ;  but  they  bear  on  their  outer  sides,  near  the 
base,  a  pair  of  other  organs,  which  are  more  closely 
analogous  to  what  we  ourselves  possess.  You  see  on  each 
tentacle  a  little  wart,  which,  when  you  look  at  it  with 
a  lens,  you  perceive  to  have  a  round  black  glossy  ex- 
tremity. This  is  the  eye.  By  careful  dissection  under 
the  microscope,  we  find  it  to  contain  a  beautiful  trans- 
parent crystalline  lens,  with  a  thick  and  glutinous  vitreous 
humour  adhering  to  it  behind,  bounded  by  a  retina  or 
curtain  to  receive  the  optic  image,  and  an  optic  nerve. 

But  much  more  attractive  you  will  find  the  eyes  in  this 
little  Scallop.  It  is  a  half-grown  individual  of  what  is 
provincially  known  as  the  Squin  (Pecten  opercularis), 
much  prized  for  its  delicate  flavour.  Belonging  to  the 
bivalve  class  of  the  Mollusca,  the  animal  is  inclosed 
within  two  shallow  shelly  plates,  concave  internally  and 
convex  externally,  which  are  united  by  a  hinge,  just  as  the 
works  of  a  watch  are  protected  by  the  case.  When  the 
little  creature  is  at  its  ease,  as  when  the  water  is  pure  and 


MOLLUSCA  I    THEER   EYES.  51 

clear,  it  lies  on  one  side,  its  valves  being  separated  as  we 
see  them  now,  a  quarter  of  an  inch  or  so  apart,  allowing 
us  to  discern  what  is  contained  between  them. 

Well,  we  see  first  a  number  of  slender  white  pointed 
threads,  peeping  out  from  each  valve,  and  spreading  on 
all  sides,  waving  hither  and  thither,  groping,  now  contract- 
ing, now  expanding,  with  incessant  but  deliberate  motion. 
These  are  tentacles.  If  we  trace  them  to  their  origin,  we 
find  them  attached  to  a  fleshy  sort  of  veil  that  lines  each 
valve  to  near  its  edge,  and  then  abruptly  falls  at  an  angle 
towards  the  opposite  valve,  where  it  meets  a  correspond- 
ing veil.  These  two  veils  form  the  mantle.  It  is  from 
each  of  these  that  the  tentacles  spring;  and  we  discover 
that  there  are  four  rows  of  these  organs,  one  row  set  along 
the  angle,  and  one  along  the  edge,  of  each  veil. 

But  as  we  peer  among  these  slender  threads,  our  atten- 
tion is  riveted  by  some  tiny  points  that  are  seated  near 
their  bases,  which  glitter  like  brilliant  gems.  They  are 
seen  only  in  those  rows  of  tentacles  which  spring  from 
the  angles  of  the  veils,  and  not  in  those  which  fringe  their 
edges.  Even  the  unassisted  sight  can  detect  the  gleam 
and  glitter  of  these  little  specks ;  but  it  is  only  when  we 
bring  the  lens  to  bear  upon  them  that  we  see  all  their 
beauty.  Then  they  look  like  diamonds  or  emeralds,  each 
set  in  a  broad  ring  of  dark  red  substance,  which  greatly 
enhances  their  beauty.  They  are  inserted  into  the  mantle 
in  the  line  of  the  tentacles,  alternating  with  them,  yet  not 
with  absolute  regularity,  for  there  are  more  tentacles  than 
gem-points  ;  they  are  about  half  as  numerous  again  as  the 
radiating  ridges  of  the  shell.  Some  are  much  larger  and 
more  prominent  than  others,  but  they  have  all  the  same 
structure  and  appearance. 

These  little  organs  are  eyes.  As  its  movements  are 
far  more  extensive,  and  more  fitful  and  rapid  than  is 
common  in  this  class  of  animals,  the  little  Pecten  probably 
needs  these  brilliant  organs  of  vision  to  guide  its  wayward 

E2 


52  EVENINGS   AT    THE    MICBO SCOPE. 

rovings,  as  well  as  to  guard  it  from  hostile  assaults.  The 
animal  is  very  sensitive,  withdrawing  its  tentacles  and 
mantle,  and  bringing  the  valves  of  its  shell  together,  on 
any  shock  being  given  to  the  vessel  in  which  it  resides.  It 
manifests,  however,  a  wisely  measured  degree  of  caution, 
for  it  does  not  actually  close  the  valves,  unless  it  be 
repeatedly  disturbed,  or  unless  the  shock  be  violent,  con- 
tenting itself  with  narrowing  the  opening  to  the  smallest 
space  appreciable  ;  yet  even  then  the  two  rows  of  gem-like 
eyes  are  distinctly  visible,  peeping  out  from  the  almost 
closed  shell,  the  two  appearing  like  one  undulating  row 
from  the  closeness  of  their  proximity. 

If  you  are  familiar  with  the  pin -cushions  which  children 
often  make  with  a  narrow  ribbon  round  the  edges  of  these 
very  Scallop-shells,  you  can  scarcely  fail  to  be  struck  with 
the  resemblance  borne  by  the  living  animal  to  its  homely 
but  useful  substitute  ;  and  the  beautiful  eyes  themselves 
might  be  readily  mistaken  for  two  rows  of  diamond- 
headed  pins,  carefully  and  regularly  stuck  along  the  two 
edges  of  the  pin-cushion  ribbon, — the  ribbon  itself  repre- 
senting the  satiny  and  painted  mantle.  A  friend  of  mine, 
to  whom  I  was  once  showing  this  object,  compared  it,  not 
inaptly,  to  a  lady's  ring  set  with  diamonds. 

You  will  not  fail  to  remark  how  the  position  of  these 
beauteous  organs  is  suited  for  their  most  extensive 
usefulness  consistent  with .  their  safety.  In  the  ordinary 
condition  of  the  animal's  expansion,  and  especially  when 
it  is  about  to  make  its  sudden  and  vigorous  leaps,  the  gem- 
like  points  are  so  situated  as  just  to  project  beyond  the 
margin  of  the  shell.  So  that  when  we  view  the  creature 
perpendicularly  as  it  lies,  our  eyes  looking  down  on  the 
convexity  of  the  upper  valve,  the  minute  eyes  are  seen,  all 
round  its  circumference,  just,  and  but  just,  peeping  from 
under  its  edge.  It  is  clear  that  this  arrangement  secures 
to  them  the  widest  range  of  vision  with  the  least  possible 
exposure.  As  Divine  contrivance  has  been  often  most 


MOLLUSCA  I    THEIR   EYES.  53 

deservedly  recognised  in  the  projection  of  the  bony  ridge 
over  the  human  eye,  which  we  call  the  brow,  we  surely 
cannot  fail  to  recognise,  and  admire  it  also,  in  the  position 
of  these  delicate  organs,  either  beneath  the  margin  of  the 
solid  shell,  or,  if  projected,  projected  only  in  the  smallest 
degree,  and  endowed  with  the  power  of  retreating  beneath 
its  barrier  with  the  rapidity  of  thought  on  the  least  alarm. 

There  can  be  no  doubt  that  these  points,  numerous  as 
they  are,  are  true  eyes,  endowed  with  the  faculty  of  vision 
in  a  well-developed  degree.  For  when  their  structure  is 
carefully  examined  by  the  skilful  anatomist,  each  is  found 
to  be  covered  with  the  proper  sclerotic*  tunic,  which 
becomes  a  perfectly  transparent  cornea  in  front,  and  to 
possess  a  coloured  iris, — perforated  with  a  well-defined 
pupil,  and  connected  with  a  layer  of  pigment  which  lines 
the  choroid  tunic, — a  crystalline  lens,  and  a  vitreous 
humour  for  the  due  refraction  of  the  rays  of  light,  and  a 
retina  in  their  focus,  formed  by  an  expansion  of  the  optic 
nerve,  and  fitted  to  receive  the  picture ;  the  sensation  of 
which  is  then  conveyed  by  an  optic  nerve  from  each  eye 
to  the  common  nerve-trunk  which  runs  along  the  border 
of  the  mantle.  Thus  there  exists  in  each  of  these  lus- 
trous points  every  element  needful  for  the  due  performance 
of  vision;  though,  probably,  the  impressions  thus  con- 
veyed may  be  neither  so  powerful  nor  so  distinct  as  those 
which  are  conveyed  by  the  eyes  of  vertebrate  animals. 
They  are,  however,  we  may  be  sure,  amply  sufficient  for 
the  wants  of  the  pretty  Scallop,  and  are  fresh  proofs  of 
the  Divine  wisdom  and  benevolence. 

We  have  been  accustomed  from  childhood  to  recognise 
as  eyes  the  shining  black  extremities  of  the  upper  pair  of 
"  horns"  in  the  Garden  Snail.  And  though  some  natu- 

*  The  ball  of  the  eye  is  composed  of  three  coats  or  tunics,  the 
sclerotic,  choroid,  and  retina,  and  contains  three  humours,  the  aqueous, 
vitreous,  and  crystalline.  The  cornea  is  the  front  part  of  the  sckrotic, 
the  iris  that  of  the  choroid. 


54  EVENINGS    AT    THE    MICROSCOPE. 

ralists  have  doubted,  and  even  denied,  that  the  tentacle 
was  anything  more  than  a  very  delicate  organ  of  touch, 
yet  it  has  been  abundantly  proved  by  dissection,  and  is 
now  incontrovertibly  established,  that  its  tip  carries  an 
eye,  even  more  completely  developed  than  those  of  the 
Pecten  which  we  have  just  been  looking  at.  The  eye  is 
situated,  not  indeed  on  the  very  summit  of  the  tentacle, 
but  on  one  side  of  a  movable  bulb  there  placed.  It  is 
very  minute,  almost  spherical,  but  slightly  flattened  in 
front.  It  is  protected  by  a  very  thin  transparent  layer  of 
the  common  skin,  and  is  surrounded  at  the  side  and 
behind  by  a  perfectly  black  membrane,  called  the  choroid, 
or  pigment-membrane.  This  black  globule  contains  a 
transparent  and  semi-fluid  substance,  with  which  it  is 
completely  filled;  towards  the  bottom  it  is  of  thinner 
consistence,  and  appears  to  contain  many  brilliant  particles 
when  the  eye  is  dissected  under  the  microscope  ;  this  may 
be  considered  as  the  vitreous  humour.  In  the  front  part 
of  the  eye  there  is  a  crystalline  lens,  a  small,  circular, 
flattish  body,  shaped  like  a  lens,  perfectly  clear  and  trans- 
lucent, but  a  little  more  solid  than  the  vitreous  humour. 

Now  protection  for  these  so  delicate  organs  is  provided 
in  a  way  quite  different  from,  yet  equally  effective  with, 
that  which  we  just  now  admired  in  the  case  of  the  Pecten. 
You  know  that  if  you  touch,  though  ever  so  tenderly,  the 
eye  of  the  Snail,  it  is  instantly  drawn  into  the  horn  by  a 


STBTJCTTTRB  OP   ETB   OF  SNAIL. 


most  curious  process  of  inversion.     This  action  is  per- 
formed by  means  of  a  long  muscular  ribbon,  which  origi- 


MOLLUSCA:  THEEB  EAES.  55 

nates  from  the  great  muscle  that  retracts  the  head  within 
the  shell,  and  which  is  inserted  into  the  extremity  of  the 
hollow  tentacle.  When  this  ribbon  contracts  at  the  will 
of  the  animal,  and  still  more  forcibly  when  it  is  aided  by 
the  contraction  of  the  great  head-mnscle,  the  tip  of  the 
tentacle  with  its  eye  is  drawn  within  the  surrounding  parts, 
just  like  the  finger  of  a  glove.  When  the  animal  would 
again  protrude  its  eye,  the  fibres  which  surround  the 
tentacle,  like  so  many  rings  throughout  its  whole  length, 
successively  contract,  and  thus  gradually  squeeze  out,  as 
it  were,  the  inverted  part,  until  it  is  turned  back  to  its 
original  position. 

But  the  ears  of  this  homely  "creeping  thing"  are, 
perhaps,  even  more  curious  than  its  eyes,  though  far  less 
elaborate  in  their  structure.  You  will  imagine  now,  that 
I  refer  to  the  other  pair  of  tentacles,  as  you  are  accus- 
tomed to  associate  the  idea  of  ears  with  projecting  organs 
situated  on  the  head.  No,  you  must  not  look  there  for 
them.  Here,  in  this  young  Garden  Slug,  which  is  so 
small  as  to  be  conveniently  examined  on  the  stage  of  the 
microscope,  and  so  devoid  of  colour  that  we  can  readily 
look  through  its  tissues, — we  shall  easily  find  its  ears, 
though  they  are  not  quite  so  prominent  as  those  of 
an  ass. 

I  subject  the  animal  to  a  gentle  pressure  by  means  of 
the  compressorium,*  just  sufficient  to  flatten  its  soft  body 
a  little,  without  injuring  it.  And  now,  with  this  low  power, 
you  may  see  what  Siebold,  a  learned  zoologist  and  com- 
parative anatomist,  familiar  with  the  curious  phenomena 
of  life,  truly  calls  "  a  wonderful  spectacle."  In -the  neck 
of  the  little  animal  you  discern,  deep-seated  in  the  soft 
flesh,  a  pair  of  perfectly  transparent  globules,  or  capsules, 
without  any  opening,  but  filled  with  a  clear  fluid,  in  which 
there  are  some  minute  bodies  performing  the  most  extra- 

*  An  instrument  for  compressing  or  flattening  an  object  under  the 
microscope. 


56  EVENINGS    AT    THE    MICROSCOPE. 

ordinary  evolutions.  They  constantly  keep  up  a  series  of 
swinging  or  balancing  movements,  sometimes  rotating, 
.sometimes  forcibly  driven  in  a  certain  direction,  then  in 
the  opposite,  yet  no  single  one  ever  by  any  accident 
touching  the  walls  of  the  capsule  in  which  they  are  con- 
tained. If  the  capsule  be  ruptured,  the  motions  instantly 
cease.  These  little  bodies  are  of  a  calcareous  nature ; 
and  they  are  called  otolithes,*  that  is,  ear-stones.  The 
most  that  we  know  of  these  curious  capsules,  which 
are  indubitably  ascertained  to  be  organs  of  hearing,  we 
owe  to  the  observations  of  the  eminent  zoologist  just 
named,  and  of  this  you  may  perhaps  like  to  learn  a 
little. 

Siebold  says  that  a  concentric  depression  is  evident  in 
these  otolithes,  and  that  there  may  be  seen  in  the  centre 
of  the  greater  number  of  them  a  shaded  spot,  or  rather  a 
minute  aperture,  which  penetrates  through  the  concretion 
from  the  one  flattened  surface  to  the  other.  Subjected  to 
a  strong  pressure,  the  otolithes  crack  in  radiating  lines, 
separating  often  into  four  pyramidal  pieces.  This  separa- 
tion also  ensues,  after  a  longer  time,  when  the  otolithes 
are  immersed  in  diluted  nitric  acid ;  and,  if  we  touch  them 
with  the  concentrated  acid,  they  suddenly  dissolve  with 
the  disengagement  of  a  gas,  whence  Siebold  concludes 
them  to  be  composed  of  carbonate  of  lime.  The  size  of 
the  otolithes  is  not  equal,  and  in  the  same  capsule  there 
are  always  some  which  are  smaller  than  others.  Within 
the  capsule  they  have,  during  life,  a  very  remarkable,  and 
in  some  respects  peculiar,  lively,  oscillatory  movement, 
being  driven  about  as  particles  of  any  light  insoluble 
powder  might  be  in  boiling  water.  The  otolithes  in  the 
centre  have  the  appearance  of  being  pressed  together  so 
as  to  form  a  sort  of  solid  nucleus,  and  towards  this  centre 
the  otolithes  near  the  circumference  seem  even  to  be 

*  From  the  Greek  o5s  (ous),  genitive  wrbs  (otos),  an  ear,  and  Atflos 
(lithos),  a  stone. 


MOLLUSCA  I    THEIR   EARS.  67 

violently  urged,  their  centripetal  rush  being  invariably 
repulsed,  and  as  often  driven  again  into  a  centrifugal  direc- 
tion. Removed  from  the  capsule,  the  motions  of  the 
otolithes  instantly  cease.  The  cause  of  these  curious 
oscillations  remains  undiscovered.  Siebold  could  detect 
no  vibratile  cilia  on  the  surfaces  of  the  capsule,  and  the 
cessation  of  the  motion  when  the  otolithes  are  removed, 
proves  them  to  be  unciliated  themselves,  and,  at  the  same 
time,  distinguishes  the  motion  from  that  of  inorganic 
molecules. 

It  has  been,  however,  more  recently  ascertained  that 
the  movements  of  the  otolithes  are  due  to  very  minute 
cilia  with  which  the  interior  surface  of  the  capsule  is 
covered.  This  had  been  long  suspected,  and  some  eminent 
physiologists,  as  Wagner  and  Kolliker,  have  distinctly 
seen  the  cilia  themselves. 

If  you  ask  what  can  be  the  use  of  ears  to  a  class  of 
animals  which  are  invariably  dumb,  I  answer  that  though 
this  is  true  with  respect  to  the  great  majority,  yet  it  may 
be  only  that  our  senses  are  too  dull  to  perceive  the  delicate 
sounds  which  they  utter,  and  which  may  be  sufficiently 
audible  to  their  more  sensitive  organs  ;  and  besides,  some 
Mollusca  can  certainly  emit  sounds  audible  by  us.  Two 
very  elegant  species  of  Sea-slug,  viz.,  Eolis  punctata, 
and  Tritonia  arlorescens,*  certainly  produce  audible  sounds. 
Professor  Grant,  who  first  observed  the  interesting  fact  in 
some  specimens  of  the  latter  which  he  was  keeping  in  an 
aquarium,  says  of  the  sounds,  that  "they  resemble  very 
much  the  clink  of  a  steel  wire  on  the  side  of  the  jar, 
one  stroke  only  being  given  at  a  time,  and  repeated  at 
intervals  of  a  minute  or  two ;  when  placed  in  a  large 
basin  of  water  the  sound  is  much  obscured,  and  is  like 
that  of  a  watch,  one  stroke  being  repeated,  as  before, 
at  intervals.  The  sound  is  longest  and  oftenest  repeated 
when  the  Tritoniae  are  lively  and  moving  about,  and  is  not 
*  Now  called  Dendronotus  arborescens. 


58  EVENINGS    AT    THE    MICROSCOPE. 

heard  when  they  are  cold  and  without  any  motion ;  in  the 
dark  I  have  not  observed  any  light  emitted  at  the  time  of 
the  stroke  ;  no  globule  of  air  escapes  to  the  surface  of  the 
water,  nor  is  any  ripple  produced  on  the  surface  at  the 
instant  of  the  stroke  ;  the  sound,  when  in  a  glass  vessel,  is 
mellow  and  distinct."  The  Professor  has  kept  these 
Tritoniae  alive  in  his  room  for  a  month,  and  during  the 
whole  period  of  their  confinement  they  have  continued  to 
produce  the  sounds  with  very  little  diminution  of  their 
original  intensity.  In  a  small  apartment  they  are  audible 
at  the  distance  of  twelve  feet.  "  The  sounds  obviously 
proceed  from  the  mouth  of  the  animal ;  and  at  the  instant 
of  the  stroke,  we  observe  the  lips  suddenly  separate,  as  if 
to  allow  the  water  to  rush  into  a  small  vacuum  formed 
within.  As  these  animals  are  hermaphrodites,  requiring 
mutual  impregnation,  the  sounds  may  possibly  be  a  means 
of  communication  between  them ;  or,  if  they  are  of  an 
electric  nature,  they  may  be  the  means  of  defending  from 
foreign  enemies  one  of  the  most  delicate,  defenceless,  and 
beautiful  Gasteropods  that  inhabit  the  deep."* 

*  Edinb.  Phil.  Journ.,  xiv.  186. 


SEA-MATS    AND    SHELLY   CORALLINES.  59 


CHAPTER  IV. 

SEA-MATS   AND    SHELLY   CORALLINES. 

WHEN  we  were  at  the  sea-side  last  summer  we  bought, 
you  may  remember,  of  a  poor  widow  whom  we  met  on  the 
beach,  a  little  basket  of  dried  sea-weeds. 

Now  all  of  those  objects  were  not  sea- weeds.  I  mean 
they  were  not  all  plants ;  some  of  them  are  animals,  and 
these  I  wish  to  bring  under  your  notice  this  evening  for 
our  microscopical  entertainment.  Here  are  exquisitely 
delicate  crimson  leaves,  as  thin  or  thinner  than  the  thin- 
nest tissue  paper,  with  solid  ribs  and  sinuous  edges.  Here 
is  a  tall  and  elegant  dark  red  feather,  quite  regularly  pin- 
nated. Here  is  a  tuft  of  purple  filaments  as  "  fine  as 
silkworm's  thread."  And  here  is  a  broad  irregular  expanse 
of  the  richest  emerald  green,  crumpled  and  folded,  yet  as 
glossy  as  if  varnished. 

Well,  all  of  these  are  plants,  certainly :  they  are  veri- 
table Alga,  or  sea- weeds.  But  here  are  other  plant-like 
objects  of  a  pale  brown,  drab,  or  snowy-white  hue.  Let 
us  take  this  flattened  brown  leaf,  divided  into  irregular 
broad  lobes ;  it  looks  almost  like  a  thickish  paper,  and  is 
about  as  flexible.  But  pass  your  finger  over  it,  and  you 
feel  that  its  surface  is  evenly  roughened ;  and  on  close  and 
careful  scrutiny  you  discern,  even  by  the  naked  eye,  that 
its  surface  is  covered  with  a  delicate  network  of  minute 
shallow  cells. 

"  Broad  Horn  wrack,"  and  "  Leafy  Sea-mat,"  are  the 
names  which  the  old  collectors  gave  to  this  object ;  and 


60  EVENINGS    AT    THE    MICROSCOPE. 

modern  naturalists  have  given  it  the  scientific  appellation 
of  Flustrafoliacea,  and  arranged  it  in  the  class  Polyzoa,  a 
group  of  animate  beings,  which  have  much  of  the  form  of 
Polypes,  and  much  of  the  structure  of  Mollusks. 

We  cut  off  a  little  piece  from  the  end  of  one  of  the  lobes, 
and  put  this  upon  the  stage  of  the  microscope.  We  now 
see  that  the  cells  are  disposed  in  nearly  parallel  rows  ;  but 
so  that  those  of  one  row  alternate  with  those  of  the  next, 
quincunx  fashion,  the  middle  of  one  cell  being  opposite  the 
end  of  its  right  and  left  neighbours  ;  or  like  the  meshes  of 
a  net.  The  cells  extend  over  the  whole  leaf,  and  are  spread 
over  both  its  surfaces  in  this  case  ;  the  united  depth 
of  two  cells  constituting  the  thickness  of  the  leaf-like 
structure.  There  are  other  species,  more  delicate,  which 
have  but  a  single  series  of  cells,  all  opening  on  the  same 
side  of  the  leaf. 

Each  individual  cell  is  shaped  like  a  child's  cradle  ;  and 
if  you  will  imagine  20,000  wicker  cradles  stuck  together 
side  by  side  in  one  plane,  after  the  quincunx  pattern  I 
have  just  mentioned  ;  and  then  the  whole  broad  array 
turned  over,  and  20,000  more  glued  on  to  these,  bottom 
to  bottom, — you  will  have  an  idea  of  the  framework  of  this 
pale-brown  leaf;  dimensions,  of  course,  being  out  of  the 
consideration.  The  number  may  appear  somewhat  im- 
mense, yet  it  is  no  larger  than  the  ordinary  average,  as  I 
will  soon  show  you.  I  measure  off  a  square  half -inch  of 
this  leaf,  which  I  carefully  cut  out  with  scissors ;  now  with 
the  micrometer  count  the  cells  in  the  square  piece. — You 
find  60  longitudinal  rows,  each  containing  28  cells,  or 
thereabouts.  Very  well ;  a  simple  arithmetical  process 
shows  that  there  are  1,680  cells  in  this  square  half-inch  ; 
or  6,720  in  a  square  inch.  Now  this  very  specimen, 
before  I  mutilated  it,  contained  an  area  of  about  three 
square  inches  ;  which  would  give  20,160  cells.  This  is 
the  number  on  one  surface ;  the  other  contains  an  equal 
number ;  and  thus  you  see  that  I  have  not  exaggerated 


SEA-MATS   AND    SHELLY    CORALLINES.  61 

the  population  of  this  tiny  marine  city.     This,  however,  is 
by  no  means  a  specimen  of  unusual  size. 

These  cells,  which  I  compare  to  cradles,  are  of  shallow 
depth,  but  the  head-part  rises  to  a  much  greater  height 
than  the  foot.  All  round  this  elevated  portion  the  margin 
is  armed  with  short  blunt  spines,  two  on  each  side,  which 
stand  obliquely  erect,  projecting  outwards  over  the  middle 
of  the  next  cell,  which  thus,  in  concert  with  the  spines  of 
the  cell  on  the  opposite  side,  they  protect. 

If  you  search  carefully  over  the  mass  of  cells  with  this 
pocket-lens,  you  will  perceive  that  on  some  of  them  are 
seated  minute  white  globules,  which  look  like  tiny  pearls. 
These  are  not  placed  in  any  regular  order,  two  being 
sometimes  found  on  contiguous  cells,  but  generally  they 
are  scattered  at  more  or  less  remote  intervals.  If  we  now 
apply  the  microscope  to  these  appendages,  each  globule 
is  seen  to  be  flat  on  that  perpendicular  side  which  faces  the 
foot  of  the  cradle ;  and  this  flat  side  is  a  movable  door, 
with  a  hinge  along  its  lower  edge.  The  door  is  of  a 
yellow  hue  ;  the  globule  itself  being,  as  I  said,  of  a  pearly 
white  hue. 

This  is  all  that  we  can  see  in  this  dried  specimen ;  but 
if  we  had  been  fortunate  enough  to  examine  it  when  first 
it  was  torn  from  its  attachment  to  an  old  shell  at  the 
bottom  of  the  sea,  you  would  have  seen  much  more. 
And  what  would  then  have  appeared  I  will  describe  to 
you. 

Suppose,  then,  that  a  coverlid  of  transparent  skin  were 
stretched  over  each  cradle,  from  a  little  within  the  margin 
all  round,  leaving  a  transverse  opening  just  in  the  right 
place,  viz.,  over  the  pillow,  and  you  would  have  exactly 
what  exists  here.  There  is  a  crescent-form  slit  in  the 
membrane  of  the  upper  part  of  the  cell,  from  which  the 
semicircular  edge,  or  lip,  can  recede  if  pushed  from ' 
within. 

Suppose,   yet  again,   that  in   every   cradle   there  lies 


62  EVENINGS   AT    THE    MICROSCOPE. 

a  baby,  with  its  little  knees  bent  up  to  its  chin,  in  that 
zigzag  fashion  that  children,  little  and  big,  often  like 
to  lie  in.  But  stay,  here  is  a  child  moving !  Softly ! 
He  slowly  pushes  open  the  semicircular  slit  in  the  cover- 
lid, and  we  see  him  gradually  protruding  his  head  and 
shoulders  in  an  erect  position,  straightening  his  knees  at 
the  same  time.  He  is  raised  half  out  of  bed,  when  lo  ! 
his  head  falls  open,  and  becomes  a  bell  of  tentacles  !  The 
baby  is  the  tenant-polype  ! 

"  This  is  a  very  amusing  romance,"  you  say.  Nay,  it  is 
no  romance  at  all.  If  you  will  excuse  the  homeliness  of 
the  comparisons,  I  venture  to  affirm  that  a  personal  exa- 
mination of  the  creature  itself  would  justify  their  correct- 
ness, and  you  would  acknowledge  that  they  could  scarcely 
be  more  apt. 

Moreover,  the  globular  chambers  show  signs  of  life ; 
their  front  doors  suddenly  open,  gape  widely,  and  then 


LEAFY   SEA-MAT. 

(A  portion  magnified.) 


shut  with  a  snap  ;  and  presently  this  opening  and  shutting 
is  repeated.  The  meaning  of  this  action  you  will  better 
understand  when  you  see  analogous  organs  in  another 


SEA-MATS    AND    SHELLY    CORALLINES.  63 

form  of  the  same  class  of  animals.  Meanwhile,  I  will 
just  point  out  a  beautiful  though  minute  proof  of  design 
in  a  point  of  the  structure  of  the  cells  connected  with  these 
pearly  chambers.  If  you  look  closely,  you  will  see  that 
the  spines  of  the  margin  are  not  found  on  those  cells  that 
carry  the  pearls ;  and  moreover,  that  they  are  also  wanting 
on  the  approximate  edges  of  the  two  cells  that  lie  behind 
every  such  pearl-bearing  cell.  Now  the  reason  of  this 
omission  is  obvious.  The  spines  projecting  obliquely 
would  interfere  with  the  gaping  of  the  door ;  and  hence 
they  are  invariably  absent  there. 

I  happen  to  have  in  my  aquarium  a  living  individual  of 
another  species  belonging  to  the  same  class,  and  agreeing 
with  this  in  all  essential  particulars  of  structure,  though 
widely  different  in  form.  The  difference,  however,  is 
mainly  dependent  on  a  rather  unimportant  point  of  ar- 
rangement ;  for  the  cells,  instead  of  being  set  side  by  side 
and  end  to  end,  in  quincunx  fashion,  to  an  indefinite 
extent,  on  two  surfaces  of  a  plane,  are  disposed  on  one 
single  surface,  and  in  longitudinal  rows  of  two  or  three 
cells  abreast ;  thus  narrow  ribbon-like  branches  are 
formed,  which  now  and  then  divide  into  two,  then  these 
into  two  more,  and  so  on.  These  branches  thus  become 
fan-shaped,  which,  by  being  slightly  curved,  became  seg- 
ments of  funnels  ;  and  the  peculiar  elegance  of  this  coral- 
line consists  in  the  mode  in  which  these  branches  are  set 
on  the  stem,  viz.,  in  an  ascending  spiral  curve,  so  that  the 
effect  is  that  of  several  imperfect  funnels  set  one  within 
another,  but  which  yet  you  perceive,  by  turning  the  whole 
gradually  round,  to  compose  a  single  corkscrew  band  of 
successive  fans.  This  whole  structure  stands  upright  in 
its  natural  state,  like  a  little  compact  shrub  growing  from 
a  root;  and  as  a  good  many  are  commonly  associated 
together,  they  form  a  sort  of  mimic  grove,  fringing  the 
sides  of  dark  rocky  sea-pools. 

The  species  is  called  the  Corkscrew  Coralline,  or,  some- 


64  EVENINGS   AT    THE    MICEOSCOPE. 

times,  the  Bird's-head  Coralline,  the  latter  name  being 
assigned  to  it  for  a  reason  which  you  will  presently  per- 
ceive. The  appellation  by  which  it  is  known  to  naturalists 
is  Bugula  avicularia. 

We  drop  our  specimen  into  a  very  narrow  cell,  com- 
posed of  parallel  walls  of  thin  glass,  a  very  minute  flat- 
tened tank,  in  fact,  such  as  can  be  put  on  the  stage  of  the 
microscope.  Here,  bathed  in  its  native  sea-water,  as 
clear  as  crystal,  we  shall  see  it  opening  and  expanding  its 
numerous  polypides  with  the  utmost  activity  and  evident 
enjoyment. 

You  gaze  ;  but  you  know  not  what  you  see.  The  pre- 
sence of  many  lines,  representing  transparent  vessels  of 
strange  and  dissimilar  shapes,  overlying  each  other ;  and 
the  swaying  to  and  fro  of  curious  objects,  which  strike 
now  and  then  forcibly  across  the  field  of  view,  are  quite 
bewildering.  I  must  act  the  showman,  and  tell  you  what 
to  see. 

The  cells  are  oblong,  shaped  much  like  a  sack  of  corn, 
with  a  spine  ascending  from  each  of  the  upper  corners. 
Each  stands  on  the  summit  of  its  predecessor  in  the  same 
row,  and  side  by  side  with  those  of  its  fellow-rows,  in 
such  an  order  that  the  top  of  one  cell  comes  opposite  the 
middle  of  the  one  beside  it.  The  top  of  the  sack  is 
rounded,  and  appears  closed,  but  we  shall  presently  find 
an  opening  there.  The  broad  side  that  faces  inwardly  has 
a  large  elliptical  transparent  space  occupying  nearly  its 
whole  surface ;  this  is  covered  with  a  very  thin  and  elastic 
membrane,  and  answers  a  peculiar  end.  Just  below  one  of 
the  spines  that  crowns  the  summit  of  the  cell  on  one  of  the 
edges,  is  situated  a  little  lump,  to  which  is  attached,  by  a 
very  free  joint,  an  object  which  you  will  perceive  to  bear  a 
remarkable  resemblance  to  the  head  of  a  bird  of  prey.  It 
has  a  beak  strongly  hooked,  with  two  well-formed  man- 
dibles, of  which  the  lower  is  movable,  shutting  into  the 
cavity  of  the  upper ;  you  observe  it  deliberately  opening, 


SEA-MATS   AND    SHELLY   CORALLINES.  65 

like  that  of  a  bird,  only  stretching  to  an  enormous  width 
of  gape,  and  then  closing  with  a  strong  and  sudden  snap. 
Now  and  then  the  whole  head  sways  backward  and  for- 
ward on  its  joints ;  and  these  movements,  combined  with 
the  fitful  and  apparently  spiteful  snappings,  performed  by 
many  birds'  heads  scattered  about  the  branch,  are  highly 
curious  and  amusing. 

The  birds'  heads,  however,  are  not  the  living  inhabi- 
tants of  the  cells ;  they  are  not  integral  parts  of  them. 
The  cells  have  their  proper  inhabitants,  each  dwelling  in 
its  own ;  and  each  essentially  formed  on  the  same  plan  as 
the  "  baby  with  the  tucked-up  knees,"  that  makes  the 
Sea-mat  for  his  cradle-house. 

In  order  to  get  a  good  view  of  the  tenant  here,  you 
must  move  the  stage  about  till  you  find  that  the  branch  is 
presented  to  your  eye  sidewise.  Directing  your  attention 
then  to  the  lateral  edge  of  a  single  inhabited  cell,  its 
summit  is  seen  to  protrude  diagonally,  towards  the  inner 
side  (i.e.,  towards  the  axis  of  the  spire),  a  tubular  mouth 
which  is  membranous  and  contractile.  When  the  animal 
wishes  to  emerge,  this  tubular  orifice  is  pushed  out  by 
unfolding  the  integument,  and  the  tentacles  are  exposed 
to  view,  closely  pressed  into  a  parallel  bundle ;  the  un- 
folding of  the  integument  that  is  attached  at  their  base, 
goes  on  till  the  whole  is  straightened,  when  the  tentacles 
diverge  and  assume  the  form  of  a  funnel,  or  rather  that 
of  a  wide-mouthed  bell,  the  tips  being  slightly  turned  out. 
They  are  furnished  with  a  double  row  of  short  cilia  in  the 
usual  order,  one  set  working  upward,  the  other  downward. 
Their  base  surrounds  a  muscular  thick  ring,  the  entrance 
to  a  funnel-shaped  sac,  the  substance  of  which  is  granular, 
and  evidently  muscular,  for  its  contractions  and  expansions 
are  very  vigorous,  and  yet  delicate.  Into  this  first  sto- 
mach passes,  with  a  sort  of  gulp,  any  animalcule  whirled 
to  the  bottom  of  the  funnel  by  the  ciliary  vortex ;  and  from 
thence  it  is  delivered,  through  a  contracted,  but  still  rather 

p 


06  EVENINGS    AT    THE    MICROSCOPE. 

wide  gullet,  into  an  oblong  stomach,  the  lower  portion  of 
which  is  obtuse.  An  extremely  attenuated  duct  connects 
this,  which  is  probably  the  true  stomach,  with  a  globular, 
rather  small,  intestine,  which  is  again  connected  by  a 
lengthened  thread  with  the  base  of  the  cell.  By  an 
arrangement  common  to  the  ascidian  *  type  of  the  diges- 
tive function,  the  food  is  returned  from  the  intestine  into 
the  true  stomach,  whence  the  useless  parts  are  discharged 
through  a  wide  and  thick  tube  that  issues  from  it  close 
behind  the  point  where  the  gullet  enters.  This  tube 
passes  upwards  parallel  to  the  gullet,  and  terminates  by  an 
orifice  outside  and  behind  the  base  of  the  tentacles.  All 
these  viscera  are  beautifully  distinct  and  easily  identified, 
owing  to  the  perfect  transparency  of  the  walls  of  the  cell, 
the  simplicity  of  the  parts,  and  their  density  and  dark 
yellow  colour.  All  of  them  are  manifestly  granular  in 
texture,  except  the  slender  corrugated  tube  which  connects 
the  stomach  with  the  globose  intestine :  this  is  thin  and 
membranous,  and  is  doubtless,  if  I  may  judge  from  analogy, 
capable  of  wide  expansion  for  the  passage  of  the  food-pellet. 
The  sudden  contraction  of  the  polypide  into  its  cell 
upon  disturbance  or  alarm,  and  its  slow  and  gradual 
emergence  again,  afford  excellent  opportunities  for  study- 
ing the  forms,  proportions,  and  relative  positions  of  the 
internal  organs.  In  contraction,  the  globular  intestine 
remains  nearly  where  it  was,  but  the  stomach  slides  down 
into  the  cell  behind  it,  as  far  as  the  flexible  duct  will 
allow,  and  the  thick  gullet  bows  out  in  front,  showing 
more  clearly  the  separation  between  it  and  the  rectum, 
and  the  insertion  of  both  into  the  stomach.  This  retrac- 
tion is,  in  part,  effected  by  a  pair  of  longitudinal  muscular 
bands,  which  are  inserted  at  the  back  of  the  bottom  part 
of  the  cell,  and  into  the  skin  of  the  neck  below  the  ten- 

*  The  Ascidia  are  a  low  order  of  animals  growing  in  masses  in  the 
sea,  with  bodies  like  little  leathern  pouches  ;  whence  their  name,  from 
a  Greek  word  aoxbs  (askos),  meaning  pouch. 


SEA-MATS    AND    SHELLY    CORALLINES.  67 

tacles.  The  contraction  of  these  bands  draws  in  the 
integument,  like  the  drawing  of  a  stocking  within  itself, 
and  forces  down  the  viscera  into  the  cavity  of  the  cell, 
which  is  probably  filled  with  the  vital  juices. 

Besides  the  hind  bands,  there  is  one,  or  a  pair  of 
similar  muscular  bands  attached  on  each  side  of  the  front 
part  of  the  base  of  the  cell,  and  inserted  similarly  into  the 
neck.  By  watching  the  contraction  of  these,  you  will  be 
enabled  to  determine  the  use  of  the  membrane-covered 
aperture  up  the  front  of  the  cell  At  the  moment  of  the 
retraction  of  the  viscera  into  the  cell,  a  large  angular 
membrane  is  forced  outward  from  the  front  side,  which  is 
protruded  more  or  less  in  proportion  to  the  degree  of 
withdrawal  of  the  polypide ;  and  as  the  latter  emerges 
again,  the  membrane  falls  back  to  its  place.  It  is  evident, 
then,  that  this  is  a  provision  for  enlarging  the  cavity ;  the 
walls  are  horny,  and  probably  almost  inelastic ;  but  when 
the  stomach  forces  the  intestine  forward,  and  the  thick 
gullet  is  bent  outward  by  the  withdrawal  of  the  neck  and 
tentacles,  the  needful  room  is  provided  by  the  bulging  out 
of  this  elastic  membrane,  which  recovers  its  place  by  the 
pressure  of  the  surrounding  water,  when  the  pressure  of 
the  fluids  within  is  removed. 

Now,  after  watching  these  movements  of  the  polypides, 
and  the  various  structures  whose  forms  and  limits  those 
movements  reveal,  it  will  become  manifest  to  you  that 
there  is  no  visible  organic  connexion  between  the  animal 
distinctively  so  called  and  the  curious  bird's  head.  Thig 
latter  has  a  muscular  system  of  its  own,  by  means  of 
which  its  energetic  motions  are  performed ;  but  it  appears 
quite  isolated  on  the  outside  of  the  calcareous  cell,  and 
wholly  cut  off  from  the  interior  by  the  knob  on  which  it  , 
works,  and  by  the  thickness  of  the  cell  wall.  Both  knob 
and  wall  appear  quite  imperforate ;  and  yet  we  cannot  but 
presume  that  some  connexion  exists,  perhaps  through  the 
medium  of  an  exceedingly  delicate  and  subtile,  but  living 
F  2 


6o  EVENINGS   AT   THE    MICROSCOPE. 

tissue,  which  may  be  presumed  not  only  to  line,  but  also 
to  cover  the  strong  cell ;  just  as  the  strong  envelope  and 
spines  of  a  Sea-urchin  are  covered  with  a  thin  film  of  living 
flesh. 

The  functions  and  use  of  these  singular  processes  are  as 
obscure  as  their  connexions  with  the  animal.  Yet  that 
they  play  some  important  part  we  may  almost  certainly 
infer,  from  the  general  prevalence  of  similar  or  analogous 
appendages  among  the  various  forms  of  this  class.  The 
globular  pearls  which  you  lately  saw  on  the  Sea-mat  are 
but  another  form  of  bird's  head;  and  the  falling-door 
answers  to  the  opening  and  shutting  mandible.  The 
forms,  indeed,  of  these  organs  are  very  diverse,  and  some- 
times they  are  greatly  disguised.  But  what  about  their 
function  ?  More  than  one  observer  has  noticed  the 
seizure  of  small  roving  animals  by  these  pincer-like  beaks  ; 
and  hence  the  conclusion  is  pretty  general,  that  they  are 
in  some  way  connected  with  the  procuring  of  food.  But  it 
seems  to  have  'been  forgotten,  not  only  that  these  organs 
have  no  power  of  passing  the  prey  thus  seized  to  the 
mouth,  but  also  that  this  latter  is  situated  at  the  bottom 
of  a  funnel  of  ciliated  tentacles,  and  is  calculated  to  re- 
ceive only  such  minute  prey  as  is  drawn  within  the  ciliary 
vortex.  I  have  ventured  to  suggest  a  new  explanation. 
The  seizure  of  a  passing  animal,  and  the  holding  of  it  in  a 
tenacious  grasp  until  it  dies,  may  be  a  means  of  attracting 
the  proper  prey  to  the  vicinity  of  the  mouth.  The  pre- 
sence of  decomposing  animal  substance  in  water  invariably 
attracts  crowds  of  infusory  animalcules,  which  then  breed 
with  amazing  rapidity,  so  as  to  form  a  cloud  of  living 
atoms  around  the  decaying  body,  quite  visible  in  the 
aggregate  to  the  unassisted  eye ;  and  these  remain  in  the 
vicinity,  playing  round  and  round  until  the  organic  matter 
is  quite  consumed.  Now  a  tiny  worm  or  other  animal 
caught  by  the  bird's  head  of  a  Polyzoon,*  and  tightly  held, 
*  From  the  Greek  TroAus  (polus),  many,  and  £wov  (animal).  A.  name 


SEA-MATS    AND    SHELLY    CORALLINES.  69 

would  presently  die ;  and  though  in  its  own  substance  it 
would  not  yield  any  nutriment  to  the  capturer,  yet  by 
becoming  the  centre  of  a  crowd  of  busy  infusoria,  multi- 
tudes of  which  would  constantly  be  drawn  into  the  ten- 
tacular vortex,  and  swallowed,  it  would  be  ancillary  to  its 
support ;  and  the  organ  in  question  would  thus  play  no 
unimportant  part  in  the  economy  of  the  animal. 

given  to  a  certain  group  of  animals  which  are,  as  it  were,  made  up  of 
many  individuals  massed  together.  By  some  naturalists  they  are  called 
Bryozoa,  a  term  derived  from  PPVOP  (bruon),  sea-moss,  and  ^v. 


70  EVENINGS   AT    THE    MICROSCOPE, 


CHAPTER  V. 

INSECTS  :    WINGS    AND    THEIR   APPENDAGES. 

I  PROPOSE  now  to  reveal  to  you  some  of  the  microscopic 
marvels  of  the  insect  world  ;  a  race  vastly  more  populous 
than  all  of  the  other  animate  tribes  put  together ;  for  the 
most  part  so  minute  as  to  be  peculiarly  suitable  subjects 
for  our  present  investigations,  and  so  furnished  with 
elaborate  contrivances  and  exquisite  pieces  of  mechanism, 
as  to  elevate  our  thoughts  at  every  turn  to  the  majesty  of 
the  Divine  wisdom  displayed  in  the  most  minute  of  His 
creatures.  Let  us  begin  with  their  wings. 

The  most  perfect  fliers  in  existence  are  Insects.  The 
swallow  and  the  humming-bird  are  powerful  on  the  wing, 
and  rapid;  but  neither  these  nor  any  other  "  winged 
fowl"  can  be  compared  with  many  of  the  filmy- winged 
Insects.  The  common  House-fly,  for  example,  will  remain 
for  hours  together  floating  in  the  air  beneath  the  ceilings 
of  our  dwelling-rooms,  hovering  and  dancing  from  side 
to  side,  without  effort  and  without  fatigue.  It  has  been 
calculated  that  in  its  ordinary  flight  the  House-fly  makes 
about  600  strokes  with  its  wings  every  second,  and  that  it 
is  carried  through  the  air  a  distance  of  five  feet  during 
that  brief  period.  But,  if  alarmed,  the  velocity  can  be  in- 
creased six  or  seven  fold,  as  every  one  must  have  observed, 
so  as  to  carry  the  insect  thirty,  or  five  and  thirty,  feet  in 
the  second.  In  the  same  space  of  time,  observes  Mr. 
Kirby,  a  race-horse  could  clear  only  ninety  feet,  which  is 
at  the  rate  of  more  than  a  mile  in  a  minute.  Our  little 


INSECTS:  WINGS  AND  THEIB  APPENDAGES.  71 

fly,  in  her  swiftest  flight,  will  in  the  same  space  of  time  go 
more  than  the  third  of  a  mile.  Now  compare  the  immense 
difference  in  size  of  the  two  animals  (ten  millions  of  the  fly 
would  hardly  counterpoise  one  racer),  and  how  wonderful 
will  the  velocity  of  this  minute  creature  appear  !  Did  the 
fly  equal  the  race-horse  in  size,  and  retain  its  present 
powers  in  the  ratio  of  its  magnitude,  it  would  traverse  the 
globe  with  the  rapidity  of  lightning.* 

Bees,  again,  are  accomplished  masters  of  aerial  motion. 
The  Humble-bees,  notwithstanding  their  heavy  bodies,  are 
the  most  powerful  fliers  of  this  class.  The  same  excellent 
entomologist  tells  us  that  they  traverse  the  air  in  segments 
of  a  circle,  the  arc  of  which  is  alternately  to  right  and  left. 
The  rapidity  of  their  flight  is  so  great  that  could  it  be  cal- 
culated, it  would  be  found,  the  size  of  the  creature  con- 
sidered, far  to  exceed  that  of  any  bird,  as  has  been  proved 
by  the  observations  of  a  traveller  in  a  railway  carriage  pro- 
ceeding at  the  rate  of  twenty  miles  an  hour,  which  was 
accompanied,  though  the  wind  was  against  them,  for  a 
considerable  distance  by  a  Humble-bee  (Bombus  subinter- 
ruptus),  not  merely  with  the  same  rapidity,  but  even 
greater,  as  it  not  unfrequently  flew  to  and  fro  about  the 
carriage,  or  described  zigzag  lines  in  its  flight.  The 
aerial  movements  of  the  Hive-bee  are  more  distinct  and 
leisurely.! 

You  have  doubtless  often  admired  the  noble  Dragon- 
fly, with  its  four  ample  and  wide-spread  wings  of  gauze, 
hawking  in  a  green  lane  or  over  a  pool  in  the  noon  of 
summer.  It  sails,  or  rather  shoots  with  arrowy  fleetness 
hither  and  thither,  now  forwards,  now  backwards,  now  to 
the  right,  now  to  the  left,  without  turning  its  body,  but 
simply  by  the  action  of  its  powerful  and  elegant  wings. 
Leeuwenhoek  once  saw  an  insect  of  this  tribe  chased  by  a 
swallow  in  a  menagerie  a  hundred  feet  long.  The  Dragon- 
fly shot  along  with  such  astonishing  power  of  wing,  to  the 
*  "  Intr.  to  Entom."  ;  Lett.  xxii.  f 


72  EVENINGS    AT    THE    MICROSCOPE. 

right,  to  the  left,  and  in  all  directions,  that  this  bird  of 
rapid  flight  and  ready  evolution  was  unable  to  overtake 
and  capture  it,  the  insect  eluding  every  attempt,  and  being 
in  general  fully  six  feet  in  advance  of  the  bird.  A  Dragon- 
fly has  been  known  to  fly  on  board  a  ship  at  sea,  the 
nearest  land  being  the  coast  of  Africa,  five  hundred  miles 
distant,  a  fact  highly  illustrative  of  its  power  of  wing. 

It  is  a  point  of  interest  to  know  the  structure  of  the 
organs  by  which  such  results  are  accomplished,  and  there- 
fore we  will  devote  an  hour  to  the  microscopical  examina- 
tion of  the  wings  of  one  or  two  insects.  Let  us  begin 
with  the  common  Fly,  one  of  which,  a  fine  blue-bottle,  is 
somewhat  noisily  buzzing  in  the  window ; — 

"  The  blue-fly  sung  i'  the  pane,"— 

as  if  to  invite  our  attention  to  him.  Well,  we  will  borrow 
one  of  his  wings  for  the  lesson  ;  and,  putting  it  into  the 
stage-forceps,  we  shall  be  able  to  turn  it  in  any  direction 
for  observation  beneath  the  microscope. 

At  first  it  seems  a  very  thin  transparent  membrane,  of  a 
shape  between  triangular  and  oval,  with  a  few  fine  black 
lines  running  through  it,  and  along  one  edge.  But  on 
bringing  a  greater  magnifying  power  to  bear  on  it,  we  see 
that  the  clear  surface  is  covered  with  minute  short  stiff 
hairs,  each  of  which  has  an  expanded  base.  And  still 
further,  by  delicate  focussing,  we  find  that  there  are  two 
sets  of  these  hairs,  which  come  into  view  alternately,  those 
of  one  row  projecting  upward  towards  our  eye,  those  of  the 
other  downward.  They  are  placed  on  both  the  upper  and 
under  surfaces,  and  are  in  fact  appendages  of  two  distinct 
membranes,  applied  to  each  other.  There  is  some  reason 
to  believe  that  these  hairs  are  delicate  organs  of  touch 
communicating  impressions  through  the  skin  to  a  sensitive 
layer  beneath ;  at  least  such  seems  their  function  on  the 
body,  and  we  may  judge  from  analogy  that  it  is  not 
different  here. 


INSECTS  I    WINGS   AND    THEIR   APPENDAGES.  78 

The  black  lines  are  elastic,  horny  tubes,  over  which  the 
membranes  are  spread  and  stretched,  like  the  silk  of  an 
umbrella  by  its  ribs.  The  upper  membrane  is  firmly 
attached  to  the  tubes  (which  are  called  nervures) ;  the 
lower  has  but  a  slight  adhesion,  and  is  easily  stripped 
from  them.  The  nervures  originate  in  the  body,  and  di- 
verge like  a  fan  to  various  points  of  the  tip,  and  to  the 
upper  and  lower  edges ;  some  of  them,  however,  terminate 
in  the  substance  of  the  wing  without  reaching  the  edge, 
and  some  send  off  cross  branches  by  which  two  are  con- 
nected together.  They  generally  maintain  the  same 
thickness  throughout,  but  there  are  enlargements  where 
the  branches  join  the  main  trunks.  These  nervures  are 
hollow,  and  are  during  life  filled  with  a  subtle  fluid,  which 
is  supplied  from  the  vessels  of  the  body.  They  contain 
also  ramifications  of  the  exquisite  spiral  air-vessels,  which 
we  shall  presently  consider,  so  that  both  air  and  blood 
circulate  in  them. 

In  this  wing  of  the  Bee  all  of  these  structures  may  be 
seen  to  greater  advantage.  The  membrane  appears  per- 
fectly uniform  by  transmitted  light,  even  with  so  high  a 
magnifying  power  as  600  diameters,  at  least  on  a  cursory 
examination;  though,  by  careful  manipulation,  we  may 
discern  faint  traces  of  angular  lines  which  divide  the  whole 
surface  into  irregular  areas.  But  by  using  reflected  light 
at  an  oblique  angle,  this  areolation,  which  indicates  the 
primary  cells  of  the  structure,  is  much  plainer,  and  each 
area  is  perceived  to  carry  a  single  hair  in  its  centre. 

The  hairs  themselves  here  take  the  character  of  curved 
spines,  not  unlike  those  of  a  rose-tree.  Along  the  front 
edge  of  the  wing  they  are  straight,  stout,  densely  crowded, 
and  overlapping  in  an  inclined  position ;  but  the  most 
interesting  modification  of  these  organs  is  seen  at  the  front 
edge  of  the  posterior  pair.  Unlike  the  Fly,  which  has  but 
a  single  pair  of  wings,  the  Bee  has  two  pairs,  of  which  the 
fore  pair  is  the  larger  and  more  horny,  the  hinder  pair 


74 


EVENINGS   AT   THE    MICROSCOPE. 


seeming  to  be,  as  it  were,  cut  out  of  the  hinder  and  inner 
side  of  the  fore  ones.     The  two  edges — the  hinder  edge  of 

the  fore  pair  and  the 
front  edge  of  the  hind 
pair  —  then  corre- 
spond, but  it  is  neces- 
sary that,  during  flight, 
when  the  wings  are  ex- 
panded, the  two  wings 
on  each  side  should 
maintain  this  relative 
position,  neither  over- 

.-  ^     ^         -    ^~    —  .    - ,         lapping  the  other,  but 
'  together      presenting 

DOUBLING  AND  HOOKS  IN  A  BEE<S  WING.      ^    ^^    g^fo^ 

wherewith  to  beat  the 

air.  There  must  be,  therefore,  some  contrivance  for  lock- 
ing together  the  two  edges  in  question,  which  yet  shall 
be  capable  of  being  unlocked  at  the  pleasure  of  the 
animal ;  for  the  wings  during  repose  slide  over  one 
another.  This  contrivance  is  furnished  by  a  series  of 
hairs  or  spines  running  along  the  front  edge  of  the  hind- 
wing;  they  are  bent  up  into  strong  semicircular  hooks, 
arching  outwards,  looking,  under  a  high  power,  like  the 
hooks  on  a  butcher's  stall.  On  the  other  hand,  the  margin 
of  the  fore-wing  is  strengthened,  and  is  turned  over  with 
a  shallow  doubling,  so  as  to  make  a  groove  into  which  the 
hooks  catch  ;  and  thus,  while  the  fore- wings  are  expanded, 
the  hooks  of  the  other  pair  are  firmly  locked  in  their 
doubled  edge,  while,  as  soon  as  flight  ceases,  and  the 
wings  are  relaxed,  there  is  no  hindrance  to  the  sliding  of 
the  front  over  the  hind  pair. 

The  wings  of  many  insects  are  interesting  on  account  of 
the  organs  with  which  they  are  clothed.  A  familiar  ex- 
ample is  furnished  by  the  common  Gnat,  a  wing  of  which 
is  on  the  slide  now  before  us.  There  is  the  same  general 


INSECTS  I    WINGS   AND    THEIR   APPENDAGES.  75 

structure  as  before, — two  clear  elastic  membranes  stretched 
over  slender  horny  tubular  nervures,  and  studded  on  both 
surfaces  with  short  spine-like  hairs,  which  in  this  case, 
however,  are  very  numerous  and  minute.  But  along  the 
nervures,  and  along  other  lines  which  run  (generally) 
parallel  with  the  front  margin,  and  also  along  the  whole 
margin,  there  are  set  long  leaf-like  scales  of  very  curious 
appearance  and  structure. 

Confining  our  attention  to  one  of  these  lines,  suppose 
one  of  the  nervures,  we  see  that  its  course  is  marked  on 
the  upper  membrane  by  five  rows  of  minute  elevated 
warts,  arranged  obliquely  with  one  another.  From  each 
of  these  warts  springs  a  slender  stem,  which  gradually 
dilates  into  a  thin  leaf-shaped  plate  of  transparent  sub- 
stance, having  from  four  to  eight  or  ten  longitudinal  ribs. 
They  project  in  a  radiating  manner,  all  inclined  towards 
the  tip  of  the  wing.  The  same  line  on  the  under-surface 
carries  the  like  number  of  leaf-like  plates,  corresponding 
in  arrangement,  structure,  form,  and  direction  with  those 
on  the  upper  side. 
The  margins  of 
the  wing  all  round 
are  furnished  with 
similar  organs, 
with  this  difference, 

that     whereas     the  SCALES  ON  A  GNAT'S  WING. 

plates    along    the 

lines  are  as  it  were  cut  off  abruptly  at  their  greatest 
diameter,  the  marginal  ones  converge  again  with  a  grace- 
fully curved  outline,  to  a  fine  point :  a  form  which  is  seen 
to  the  greatest  advantage  along  the  hind  edge  of  the  wing, 
while  those  of  the  front  margin  are  thicker,  and  more 
densely  crowded. 

There  are,  however,  other  Insects  which  display  these 
or  similar  appendages  in  far  greater  profusion,  and  in 
much  variety  of  form  and  appearance.  In  the  fissures  or 


76  EVENINGS   AT    THE    MICROSCOPE. 

cliffs  that  border  the  sea- shore  may  often  be  found  some 
wingless  but  active  Insects,  which  are  endowed  with  the 
power  of  leaping  in  great  perfection.  From  their  hinder 
extremity  being  furnished  with  long  projecting  bristles,  they 
are  sometimes  called  Bristle-tails,  but  naturalists  desig- 
nate the  genus  Machilis.  If  you  can  get  one  sufficiently 
still  to  examine  it,  you  will  be  delighted  with  the  lustre  of 
its  clothing,  which  appears  dusted  all  over  with  a  metallic 
powder  of  rich  colours, — red,  brown,  orange  and  yellow, 
foiled  by  dull  lead-grey  in  places. 


BRISTLBXTAIL. 

(Slightly  enlarged.) 

If  you  touch  one  of  these  nimble  leapers,  though  ever  so 
lightly,  you  will  see  the  result  on  your  finger-ends ;  for 
they  will  be  found  covered  with  a  thin  stratum  of  the 
finest  dust,  which  displays  the  coloured  metallic  reflections 
seen  on  the  insect.  By  touching  one  with  a  plate  of  glass 
instead  of  your  finger,  you  will  get  the  same  dust  to  adhere 
to  this  transparent  medium,  by  applying  which  to  the 
microscope  you  may  at  once  discern  the  marvellous  nature 
of  the  raiment  with  which  the  little  creature  is  bedecked. 

The  dust  is  now  seen  to  be  composed  of  myriads  of  thin 
scales,  mostly  regular  and  symmetrical  in  their  forms, 
though  varying  exceedingly  among  themselves  in  this  re- 
spect. Some  are  heart-shaped,  some  shovel- shaped,  some 
round,  oval,  elliptical,  half  round,  half  elliptical,  long  and 


INSECTS  I    WINGS    AND   THEIR    APPENDAGES. 


77 


narrow,  sometimes  irregular  and  unequal,  and  of  various 
other  indescribable  outlines.  Perhaps  the  most  common 
forms  are  ovate,  heart-shaped,  and  that  of  the  pan  of  a 
fire-shovel.  Each  thin  scale  has  a  minute  foot-stalk, 
which  is  not  connected  with  it  at  either  extremity,  but  at 
a  point  of  one  surface  a  little  way  from  the  smaller  end, 
whence  it  projects  at  an  oblique  angle  ;  so  that  when  the 
stalk  was  inserted  in  its  proper  cell  in  the  skin  of  the 
insect,  the  scale  lay  horizontally,  covering  the  insertion. 
This  is  a  peculiarity  not  found  in 
some  other  scales  that  I  shall  pre- 
sently introduce  to  you. 

The  whole  body  of  the  scale  is 
traversed  by  a  series  of  fine  close- 
set  parallel  lines,  running  longitu- 
dinally from  end  to  end.  At  least 
this  is  the  ordinary  arrangement; 
but  occasionally  you  see  scales,  in 
which  there  are  two  series  of  parallel 
lines,  arranged  on  either  side  of  an 
imaginary  central  line,  towards  which 
they  respectively  converge,  but  never, 
I  think,  diverge  from  it.  These  lines 
appear  to  form  thickened  ribs,  but  seem  to  be  made  by 
elevations  of  the  membrane  both  above  and  below.  Be- 
tween the  ribs,  on  the  larger  scales,  we  see  a  number  of 
very  delicate  cross  lines,  which  are  probably  regular 
wrinklings  of  the  depressed  surface. 

There  is  another  little  Insect  of  the  same  family,  com- 
monly found  in  cupboards,  and  in  chinks  of  old  damp 
houses,  and  called  the  Sugar-louse  (Lepisma) ;  very  much 
like  this,  but  of  a  silvery  lustre,  and  carrying  the  three 
bristles  of  the  tail  diverging  widely.  This  also  is  covered 
with  scales,  some  of  which  are  preserved  on  this  glass 
slide.  Here,  while  the  general  appearance  and  structure 
agree  with  those  of  the  scales  which  we  have  just  been 


SCALE  OF   BRISTLE-TAIL. 


78  EVENINGS   AT    THE   MICEOSCOPE. 

considering,  there  is  considerable  diversity  in  details.  The 
form  is  usually  ovate  or  shovel-like ;  the  foot-stalk,  pro- 
jecting at  a  similar  angle,  is  not  set  on  the  inferior  surface, 
but  in  the  bottom  of  a  deep  narrow  incision ;  and  the  ribs 
are  invariably  divergent  like  those  of  a  fan.  In  these, 
however,  there  is  a  peculiarity  of  arrangement,  which  I 
have  never  seen  noticed,  but  which  is  obvious  enough  in 
the  specimens  before  us.  The  ribs  on  the  two  surfaces 
diverge  at  different  angles,  those  of  the  upper  surface 
being  the  more  divergent,  standing  out  widely  from  the 
foot-stalk,  while  those  of  the  lower  membrane  are  coarser, 
and  much  more  nearly  parallel,  their  bases  ranging  along 
the  hind  edge  of  the  scale.  The  effect  of  the  intersection 
of  the  sets  of  lines  at  so  acute  an  angle,  is  to  convey  the 
optical  impression  that  the  scale  is  covered  with  short 
irregular  dashes. 

Such  is  the  arrangement  on  these  scales,  which  I  pre- 
pared myself  from  the  common  Lepisma;  but  I  have  a 
slide  marked  "  Lepisma,"  from  one  of  the  dealers  in 
microscopic  objects,  in  which  the  ribs  on  the  two  sides 
concur;  but,  on  one  side,  there  are  obliquely  divergent 
lines  visible  only  near  the  margin,  which  appear  to  be  pro- 
duced by  wrinkles  of  the  membrane  analogous  to  the 
transverse  dashes  on  those  of  Machilis. 

Scales  much  more  delicate  than  either  of  these  sorts  are 
found  on  the  Podura,  a  minute  insect,  of  which  there  are 
several  species ;  which  leap,  jerking  out  the  bristles  of  the 
tail,  that  are  ordinarily  carried  under  the  body,  like  a 
coiled  spring.  They  are  common  in  cellars,  in  hot-bed 
frames,  on  dunghills,  on  the  surface  of  water  in  road-ruts, 
&c.  On  the  slide  before  you  are  some  of  the  smaller 
scales  from  one  of  these  insects;  they  are  exceedingly 
delicate,  and  the  clearness  with  which  you  discern  the 
character  of  their  markings,  is  a  proof  of  the  good  defini- 
tion of  your  microscope ;  this  is  what  is  called  a  "  test- 
object."  At  first  sight  they  seem  covered  with  ribs  like 


INSECTS  I  WINGS  AND  THEIR  APPENDAGES.      79 

those  of  the  Machilis  and  Lepisma ;  but,  by  the  use  of  a 
magnifying  power  of  600  diameters  (as  I  have  now  put  on), 
you  perceive  that,  in  the  first  place,  the  lines  are  not 
straight  nor  parallel,  but  curve  irregularly,  and  are  often 
branched;  and,  in  the  second  place,  that  they  are  not 
uninterrupted,  but  made  up  of  a  series  of  successive  wedge- 
shaped  warts,  which  lie  nearly  flat,  but  project  a  little  at 
the  larger  end,  where  each  overlaps  the  next.*  The  scale 
we  are  looking  at  measures  -0014  inch  in  length,  and 
•0009  in  width ;  here  the  marks  are  well  defined ;  here  are 
smaller  scales  -0008  in  length  by  -00085  in  width,  but 
these  are  more  dim  and  difficult  to  resolve. 

The  beautiful  and  extensive  order  called  Lepidoptera  or 
Scale-winged,  par  excellence,  including  the  gay  tribes  of 
Butterflies  and  Moths,  present  us  with  many  exceedingly 
interesting  varieties  in  these  singular  coverings.  The 
study  of  these  might  be  almost  as  wide  as  the  immensity 
of  species ;  I  can  show  you  only  a  few  examples. 

Here  are  specimens  from  the  pretty  little  white  Five- 
plume  Moth  (Pterophorus),  so  common  in  meadows  in 
summer.  The  general  shape  of  the  scales  from  the  body 
and  wings  is  that  of  a  willow-leaf,  some  singly  pointed, 
but  more  cut  at  the  tip  into  two,  three,  or  four  notches. 
Those  from  the  legs  are  longer,  and  slenderer  in  propor- 
tion;  and  among  the  others  from  the  wings,  there  are 
some  which  take  the  form  of  hairs,  which  send  forth  one 
or  more  branches  from  one  side,  that  form  a  very  acute 
angle  with  the  main  stem.  The  scales  proper  are  all 

*  Mr.  Richard  Beck,  using  illumination  under  a  power  of  1,300  dia- 
meters, with  the  binocular  microscope,  has  satisfied  himself  that  the 
markings  of  the  Podura  scale  "consist  of  a  series  of  toothed  ridges, 
the  profile  of  which  might  be  said  to  resemble  the  edge  of  a  saw."  He 
believes  that  the  markings  on  this  and  all  similar  scales  are  "  more  or 
less  elevations  or  corrugations  upon  the  surface,  which  serve  the  simple 
purpose  of  giving  strength  to  very  delicate  membranes."  (See  Quart. 
Journ.  Microsc.  Sci.  for  1862,  p.  122.)  This  verdict,  though  diversely 
expressed,  does  not  importantly  differ  from  my  own  judgment  given 
above. 


80 


EVENINGS   AT    THE    MICROSCOPE. 


marked  with  longitudinal  lines,  very  minute  and  close,  but 
they  mostly  bear  a  central  band,  and  sometimes  a  marginal 
one  on  each  side,  of  spots  set  in  sinuous  lines  like  the 
bands  on  a  mackerel's  back  ;  these  are  probably  composed 
of  pigment-granules. 

These  from  the  pretty  Six-spot  Burnet  Hawk-moth,  are 
nearly  opaque,  especially  those  from  the  red  parts  of  the 
wings,  which  have  a  rich  ruddy  glow  by  transmitted  light. 
They  are  narrow  in  shape,  tapering  gradually  forward  from 
the  foot-stalk,  and  terminate  mostly  in  two  blunt  points. 
The  ribs  are  coarse  for  the  size  of  the  scales,  and  the 
depressed  spaces  are  marked  with  irregular  pigment-grains. 

The  hairs  with  which  the  bodies  of  Moths  are  invested 
are  essentially  of  the  same  character  as  the  scales  which 
clothe  their  wings.  Here  are  examples  from  the  glowing 
sides  of  the  abdomen  of  that  -richly-  coloured  insect,  the 


You  see  they  are  simple  scales,  drawn 
out  to  an  inordinate  length  and  great 
tenuity;  each  has  its  quill-like  foot- 
stalk, and  we  may  trace  on  some  of 
them  the  ribs  and  transverse  dotting, 
while  here  we  see  all  intermediate 
stages  between  the  slenderest  hair  and 
the  broadly  ovate,  bluntly-  pointed, 
scales  from  the  wings. 

You  are  familiar  of  course  with  the 
brilliant  little  Blue  Butterfly  (Polyom- 
matus  Alexis},  which  dances  and  glit- 
ters in  the  sunshine  on  waste  places  in 
June.  Among  the  scales  of  ordinary 
form  which  clothe  the  lovely  little 
wings  will  occur  one  here  and  there  of 
a  different  shape  from  the  rest.  Here 
you  may  see  one  ;  it  is  much  smaller 
than  the  average  ;  the  foot-  stalk  is  very  long,  and  the  shape 


BATTLEDORE    SCALE    OF 
POLYOMMATU8    ALEXIS. 


INSECTS  I    WINGS    AND    THEIR   APPENDAGES. 


81 


of  the  entire  scale  is  that  of  a  battledore.  The  ribs  are 
rather  few  and  coarse,  and  they  have  this  peculiarity,  that 
each  rib  swells  at  intervals  into  rounded  dilations,  each 
of  which  has  a  minute  black  point  in  its  centre.  In  some 
of  these  battledore  seales  there  is,  near  the  lower  part 
of  the  expansion,  a  crescent  of  minute  pigment-grains. 

The  silvery  grey  surface  of  the  front  wings  of  a  common 
moth,  known  as  the  Buff-tip  (Pygara  bucephala),  is  com- 
posed of  scales  of  unusual  magnitude,  and  of  a  remarkable 
form,  their  shape  being  that  of  an  expanded  fan,  and  being 
quite  distinguishable  by  the  unassisted  eye.  The  ribs  are 
very  fine  and  numerous,  and  there  are  diverging  lines  of 
pigment-grains  running  through  the  scale. 

Those  of  the  Emperor  Moth  (Satumia  pavonia  minor) 
are  likewise  triangular  in  outline,  and  are  remarkable  for 
being  deeply  notched  at  the  end ;  so  deeply  as  to  leave 
projecting  points  (from  two  to  five)  as  long  as,  or  even 
longer  than,  the  undivided  portions  of  the  scale. 

In  some  species  we  find  scales  the 
tips  of  which  are  furnished  with  a  curi- 
ous sort  of  fringe.  This  slide  presents 
several  such  in  the  midst  of  many  of  a 
more  ordinary  shape  and  appearance. 
The  scales  in  question  are  straight,  and 
parallel- sided,  rather  narrow,  with  the 
basal  end  rounded,  and  the  terminal  ex- 
tremity tapered  abruptly  to  a  point ;  it 
is  on  each  slope  of  this  point  that  the 
fringe  is  arranged.  The  surface  does 
not  appear  to  be  elevated  in  ribs,  but 
smooth  ;  while  the  whole  interior,  except 
a  crescent  around  the  foet-staik,  is  filled 
with  pigment-grains,  imparting  a  mottled 
appearance.  It  is  remarkable  that  all 
the  scales  of  this  form  have  the  foot- 
stalk turned  in  under  the  expanse.  The  example  which 

G 


FRINGED  SCALE  OP 
PIERIS. 


82  EVENINGS    AT    THE    MICEOSCOPE. 

we  are  considering  is  from  the  white  portion  of  the  wing 
of  Pieris  Grlaucippe,  a  fine  butterfly  from  China ;  but  a 
similar  structure  is  found  in  our  own  Garden  Whites  and 
Meadow  Browns  (Pieridce  and  Satyrida). 

Scales  taken  from  the  brilliant  changeable  blue-green 
patch  in  the  hind-wing  of  Papilio  Paris,  a  fine  Indian  but- 
terfly, have  an  interesting  appearance.  They  are  simply 
pear-shaped  in  outline,  with  few  longitudinal  ribs  set  far 
apart,  and  numerous  strongly-marked  corrugations  running 
across  between  them.  That  these  are  really  elevations  of  the 
surface,  is  well  seen  in  some  scales,  even  with  transmitted 
light,  and  a  high  power ;  for  the  slopes  of  the  wrinkles 
that  face  the  light  display  the  lustrous  emerald  reflection 
proper  to  the  wing,  while  the  transmitted  colour  of  the 
whole  scale  is  a  rich  transparent  red. 

The  dimensions  of  the  scales  do  not  bear  any  certain 
proportion  to  the  size  of  the  insect  which  is  clothed  with 
them ;  those  from  the  broad  wings  of  the  noble  Saturnia 
Atlas,  for  example,  eight  or  nine  inches  in  expanse,  being 
exceeded  in  size  by  some  from  those  of  our  little  native 
Muslin  Moth,  an  inch  wide. 

You  will  say  that  what  I  am  about  to  show  you  is  a 
lovely  object ;  but  for  its  right  display  I  must  use  a  low 
magnifying  power, — not  higher  than  a  hundred  diameters, 
— with  condensed  light  falling  upon  the  surface.  It  is  a 
small  fragment  cut  from  the  wing  of  Papilio  Paris,  show- 
ing several  rows  of  the  scales  in  their  natural  arrangement. 
The  gem-like  radiance  of  the  glittering  green  scales  on  the 
black  ones,  by  which  they  are  environed,  glares  out  with  a 
splendid  effect;  and,  what  is  more  interesting,  you  can 
trace  the  manner  in  which  they  are  set, — those  of  each 
row  slightly  overlapping  the  bases  of  another  row,  like 
slates  on  a  roof, — and  also  the  mode  in  which  they  are  in- 
serted. The  clear  horn-coloured  membrane  of  the  wing  is 
seen  raised  in  shallow  transverse  steps  (if  I  may  use  such 
a  term),  so  that  if  it  were  divided  longitudinally,  the  edge 


INSECTS  I    WINGS    AND    THEIB   APPENDAGES.  83 

would  appear  cut  into  saw-like  teeth.  Along  the  margins 
of  these  ridges  are  set  minute  sockets,  which  are  very  dis- 
tinctly seen,  where  the  scales  have  been  displaced ;  in 
these  the  tiny  foot-stalks  of  the  scales  are  inserted. 

The  little  Beetles  with  which  we  are  familiar  under  the 
name  of  Weevils,  characterised  by  their  long  slender 
snouts,  at  the  end  of  which  they  carry  curiously  folding 
antennae,  and  which  constitute  the  family  CurculionidcB, 
are  in  many  cases  clothed  with  scales,  to  which  they  owe 
their  colours  and  patterns.  Several  of  our  native  species 
display  a  green  or  silvery  lustre,  which  under  the  micro- 
scope is  seen  to  be  produced  by  oval  scales.  But  these 
are  eclipsed  by  the  splendour  of  many  tropical  species ; 
especially  that  well-known  one  from  South  America,  which 
is  called  the  Diamond  Beetle,  and  scientifically  Entimus 
imperialism  from  its  unparalleled  magnificence. 

A  piece  of  one  of  the  wing-cases  of  this  beetle  is  gum- 
med to  the  slide  now  upon  the  stage.  We  look  at  it  by 
reflected  light  with  a  magnifying  power  of  130  diameters. 
We  see  a  black  ground,  on  which  are  strewn  a  profusion  of 
what  look  like  precious  stones  blazing  in  the  most  gorgeous 
lustre.  Topazes, 
sapphires,  ame- 
thysts,rubies,eme- 
ralds,  seem  sown 
broadcast;  and  yet 
not  wholly  without 
regularity , for  there 
are  broad  bands  of 
the  deep  black  sur- 
face, where  there 
are  no  gems,  and, 
though  at  consider  - 

.  SCALES  OF  DIAMOND-BEETLE. 

able    diversity    of 

angle,  they  do  all  point  with  more  or  less  precision  in  one 
direction,  viz.,  that  of  the  bands. 
G  2 


84  EVENINGS   AT    THE    MICROSCOPE. 

These  gems  are  flat  transparent  scales,  very  regularly 
oval  in  form,  for  one  end  is  rather  more  pointed  than  the 
other  ;  there  is  no  appearance  of  a  foot- stalk,  and  by  what 
means  they  adhere,  I  know  not;  they  are  evidently  at- 
tached in  some  manner  by  the  smaller  extremity  to  the 
velvety  black  surface  of  the  wing-case.  The  gorgeous 
colours  seem  dependent  in  some  measure  on  the  reflection 
of  light  from  their  polished  surface,  and  to  vary  according 
to  the  angle  at  which  it  is  reflected.  Green,  yellow,  and 
orange  hues  predominate ;  crimson,  violet,  and  blue  are 
rare,  except  upon  the  long  and  narrow  scales  that  border 
the  junctions  of  the  wing-cases,  where  these  colours  are 
the  chief  reflected.  Yet  there  appears  to  be  some  positive 
colour  in  their  substance  ;  for  in  these  latter  scales,  which, 
projecting  beyond  the  edge  of  the  wing-case,  can  be  ex- 
amined as  transparent  objects,  and  that  with  a  high 
power,  the  transmitted  light  is  richly  coloured  with  the 
same  tints  as  the  same  scales  displayed  under  the  Lieber- 
kiihn. 

We  may  derive  pleasant  instruction  from  continuing  our 
observations  on  a  few  other  wings  of  insects.  If  you  have 
ever  thought  on  the  subject,  you  have  probably  taken  for 
granted  that  the  various  sounds  produced  by  insects  are 
voices  uttered  by  their  mouths.  But  it  is  not  so.  No 
insect  has  anything  approaching  to  a  voice.  Vocal  sounds 
are  produced  by  the  emission  of  air  from  the  lungs, 
variously  modified  by  the  organs  of  the  mouth.  But  no 
insect  breathes  through  its  mouth ;  no  air  is  expelled 
thence  in  a  single  species.;  it  is  a  biting,  or  piercing, 
or  sucking  organ  ;  an  organ  for  the  taking  of  food,  or  an 
organ  for  offence  or  defence ;  but  never  an  organ  of 
Bound. 

The  wings  are  in  most  cases  the  immediate  causes  of 
insect  sounds ;  and,  in  the  case  of  the  Two-winged  Flies 
(Diptera),  Kirby  seems  to  have  shown  on  sufficient  evidence 
that  the  humming  is  produced  by  the  friction  of  the  root  or 


INSECTS  I    WINGS    AND    THEIB   APPENDAGES.  85 

base  of  the  wings  against  the  sides  of  the  cavity  in  which 
they  are  inserted.* 

There  is  a  pretty  little  beetle  (Clytus),  not  uncommon  in 
summer  in  gardens,  remarkable  for  the  brilliant  gamboge- 
yellow  lines  across  its  dark  wing-cases,  which  makes  a 
curious  squeaking  sound  when  you  take  it  in  hand.  You 
think  it  is  crying ;  but  if  you  carefully  examine  it  with  a 
lens  while  the  noise  is  uttered,  you  will  perceive  that  the 
cause  is  the  grating  of  the  thorax  against  the  front  part  of 
the  two  wing-cases.  Several  other  beetles  produce  similar 
sounds  when  alarmed,  by  rubbing  the  other  end  of  the 
wing-sheaths  with  the  tip  of  the  abdomen.  Many  of  those 
genera  which  feed  on  ordure  and  carrion  do  this. 

But  the  noisiest  of  all  insects  are  those  of  the  classes 
Orthoptera  and  Homoptera,  the  Crickets  and  Grasshoppers, 
and  the  Treehoppers.  And  these  shall  bring  us  back  to 
our  microscope,  to  which  we  shall  return  with  the  more 
zest,  after  this  little  interval  of  repose  for  our  strained 
eyes. 

Listen !  we  hear,  coming  up  the  kitchen- stairs,  the 
chirping  of  the  House-cricket  (Acheta  domestica). 

We  will  catch  one  for  investigation. 

Now,  you  see,  each  of  the  upper  wings  (or  wing-cases) 
has  a  clear  space  near  the  centre,  of  a  triangular  form, 
crossed  by  one  or  two  slender  nervures.  This  space  has 
received  the  name  of  the  tympanum  or  drum.  It  is 
bounded  externally  by  a  broad  dark  nervure,  which  with  a 
low  power  we  see  is  scored  with  three  or  four  longitudinal 
furrows,  of  course  separated  by  as  many  horny  ridges. 
In  front  of  the  clear  drum,  and  forming  a  curved  base  to 
the  triangle,  a  horny  ridge  passes  across,  tapering  out- 
wards, which  is  roughened  throughout  its  length  by  close- 
set  teeth  exactly  Like  a  file.  When  the  insect  chooses  to 
be  musical,  it  partially  opens  and  then  closes  its  wing- 

*  "  Introd.  to  Entom." ;  Lett.  xxiv.  See,  however,  the  quotation 
from  Burmeister  on  p.  91,  infra. 


86  EVENINGS   AT    THE    MICROSCOPE. 

cases,  causing  the  two  files  to  rub  across  each  other ;  and 
this  gives  rise  to  the  peculiar  ringing  vibration,  the  inten- 
sity of  which  is  heightened  by  the  tense  "  drum  "  acting  as 
a  sounding-board. 

So  at  least  some  say ;  but  M.  Goureau,  who  has  pub- 
lished some  elaborate  observations  on  the  chirping  of 
insects,*  asserts  that  the  sound  is  chiefly  owing  to  the 
action  of  the  "  file "  (which  he  calls  the  "bow")  on  the 
longitudinally -ridged  nervure,  which  he  calls  the  "  treble- 
string." 

We  see  in  this  individual  that  is  so  obliging  as  to  pro- 
duce its  chirping  before  us,  that  he  elevates  the  wing- 
sheaths  so  as  to  form  an  acute  angle  with  the  body,  and 
then  rubs  them  together  with  a  very  brisk  horizontal 
motion ;  but  which  of  the  nervures  it  is  that  actually  pro- 
duces the  sounds,  it  would  require  a  very  careful  and 
elaborate  series  of  experimental  researches  to  determine. 
It  has  been  asserted  that  the  legs-  play  a  part  in  the  music 
by  being  rubbed  against  the  bows ;  this,  however,  seems 
improbable  from  their  relative  position. 

In  the  Southern  United  States,  I  have  had  opportunities 
of  seeing  and  of  hearing  a  very  noisy  performer  of  the 
Gryllus  tribe,  called  the  Katedid  (Pterophylla  concava), 
which  sings  throughout  the  night  in  the  foliage  of  the 
trees.  The  sounds,  reiterated  on  every  side,  resemble  a 
score  or  two  of  quarrelsome  people  with  shrill  voices,  di- 
vided into  pairs,  the  individuals  of  each  pair  squabbling 
with  each  other ;  "  I  did !  "  "  You  didn't  I  "  " I  did  !  " 
"  You  didn't !  "  the  objurgation  maintained  with  the  most 
amusing  pertinacity,  and  without  a  moment's  intermission. 
Here  the  wing-sheaths,  which  are  large  and  as  it  were  in- 
flated, are  certainly  the  organs  of  sound.  A  portion  of 
each  is  turned,  at  right  angles  to  the  remainder,  over  the 
back,  so  that  the  one  partly  overlaps  the  other.  The 
musical  organ  consists  of  a  hard  glassy  ridge  in  front, 
*  "Ann.  Soc.  Ent.  de  France." 


INSECTS:  WINGS  AND  THEIB  APPENDAGES.          87 

behind  which  is  a  transparent  membrane,  which  appears 
tightly  stretched  over  a  semicircular  rim,  like  the  parch- 
ment of  a  drum,  answering  in  structure  and  in  function  to 
the  part  so  compared  in  the  Cricket. 

This  Gryllus  I  found  would  chirp  freely,  when  held  in 
my  fingers,  provided  I  held  it  by  the  head  or  thorax,  so 
as  not  to  interfere  with  the  freedom  of  the  wing-cases  : 
though  these  needed  only  to  be  partially  opened,  the  bases 
being  merely  slightly  separated  without  affecting  the  general 
contiguity.  The  two  glassy  ridges  were  rubbed  across 
each  other,  making  the  sharp  crick.  Ordinarily  this  was 
done  thrice,  three  distinct  but  rapid  crossings  making  the 
sound  represented  by  the  word  "  Katedid ;"  but  occasion- 
ally the  insect  gave  but  a  single  impulse,  uttering  as  it 
were  but  one  syllable  of  the  word. 

The  Locusts  and  Grasshoppers,  however,  do,  it  appears, 
make  use  of  their  hind  legs  in  producing  their  chirp.  If 
you  look  at  this  Grasshopper's  leg,  you  will  see  that  the 
thigh  is  marked  with  a  number  of  transverse  overlapping 
angular  plates,  and  that  the  shank  carries  a  series  of  short 
horny  points  along  each  side.  The  insect,  when  it  chirps, 
brings  the  shank  up  to  its  thigh,  and  rubs  both  to  and  fro 
against  the  wing-sheaths,  doing  this  by  turns  with  the 
right  and  left  legs,  which  causes  the  regular  breaks  in  the 
sound.  The  drum,  on  which  this  rubbing  vibrates,  has 
been  described  by  the  anatomist,  De  Geer  : — "On  each 
side  of  the  first  segment  of  the  abdomen,"  says  he,  "im- 
mediately above  the  origin  of  the  posterior  thighs,  there  is 
a  considerable  and  deep  aperture  of  rather  an  oval  form, 
which  is  partly  closed  by  an  irregular  flat  plate  or  oper- 
culum  of  a  hard  substance,  but  covered  by  a  wrinkled 
flexible  membrane.  The  opening  left  by  this  operculum  is 
semilunar,  and  at  the  bottom  of  the  cavity  is  a  white 
pellicle  of  considerable  tension,  and  shining  like  a  little 
mirror.  On  that  side  of  the  aperture  which  is  towards  the 
head  there  is  a  little  oval  hole,  into  which  the  point  of  a 


88  EVENINGS    AT   THE    MICROSCOPE. 

pin  may  be  introduced  without  resistance.  When  the  pel- 
licle is  removed,  a  large  cavity  appears.  In  my  opinion 
this  aperture,  cavity,  and  above  all  the  membrane  in 
tension,  contribute  much  to  produce  and  augment  the 
sound  emitted  by  the  grasshopper."  * 

In  this  case  we  may  without  hesitation  conclude  that 
the  friction  of  the  thigh-plates  and  shank-points  on  the 
rough-edges  of  the  wing-cases,  produces  the  musical  vibra- 
tion on  the  tense  membrane,  as  rubbing  a  wet  glass  with 
the  finger  will  yield  a  loud  musical  note. 

The  most  elaborate  contrivance  for  the  production  of 
sounds  among  the  Insect  races,  however,  is  found  among 
the  Cicadae,  celebrated  in  classical  poetry  as  the  very  im- 
personations of  song  and  eloquence.  I  regret  I  cannot 
show  you  this  apparatus  ;  for  though  we  have  a  British 
species, — lately  discovered  in  the  New  Forest, — it  is  very 
rare.  Should  you  travel,  however,  either  in  the  old  or  new 
world,  you  will  have  abundant  opportunities  of  using  your 
microscope  to  verify  the  following  description  by  our 
prince  of  entomologists,  Mr.  Kirby  : — 

"  If  you  look  at  the  under  side  of  the  body  of  a  male, 
the  first  thing  that  will  strike  you  is  a  pair  of  large  plates 
of  an  irregular  form — in  some  semi-oval,  in  others  triangu- 
lar, in  others  again  a  segment  of  a  circle  of  greater  or  less 
diameter,  covering  part  of  the  belly,  and  fixed  to  the 
trunk  between  the  abdomen  and  the  hind  legs.  These 
are  the  drum  covers  or  opercula,  from  beneath  which  the 
sound  issues.  At  the  base  of  the  posterior  legs,  just 
above  each  operculum,  there  is  a  small  pointed  triangular 
process,  the  object  of  which,  as  Reaumur  supposes,  is  to 
prevent  them  from  being  too  much  elevated.  When  an 
operculum  is  removed,  beneath  it  you  will  find  on  the  ex- 
terior side  a  hollow  cavity,  with  a  mouth  somewhat  linear,  • 
which  seems  to  open  into  the  interior  of  the  abdomen  : 
next  to  this,  on  the  inner  side,  is  another  large  cavity 
*  De  G-eer,  iii.  471. 


INSECTS  :  WINGS  AND  THEIR  APPENDAGES.       89 

of  an  irregular  shape,  the  bottom  of  which  is  divided  into 
three  portions ;  of  these  the  posterior  is  lined  obliquely 
with  a  beautiful  membrane,  which  is  very  tense — in  some 
species  semi-opaque,  and  in  others  transparent — and  re- 
flects all  the  colours  of  the  rainbow.  This  mirror  is 
not  the  real  organ  of  sound,  but  is  supposed  to  modu- 
late it.  The  middle  portion  is  occupied  by  a  plate  of 
a  horny  substance,  placed  horizontally,  and  forming 
the  bottom  of  the  cavity.  On  its  inner  side  this  plate 
terminates  in  a  carina  or  elevated  ridge,  common  to  both 
drums.  Between  the  plate  and  the  after-breast  (post- 
pectus)  another  membrane,  folded  transversely,  fills  an 
oblique,  oblong,  or  semilnnar  cavity.  In  some  species  I 
have  seen  this  membrane  in  tension ;  probably  the  insect 
can  stretch  or  relax  it  at  its  pleasure.  But  even  all  this 
apparatus  is  insufficient  to  produce  the  sound  of  these 
animals  ;  one  still  more  important  and  curious  yet  remains 
to  be  described.  This  organ  can  only  be  discovered  by 
dissection.  A  portion  of  the  first  and  second  segments 
being  removed  from  the  side  of  the  back  of  the  abdomen 
which  answers  to  the  drums,  two  bundles  of  muscles  meet- 
ing each  other  in  an  acute  angle,  attached  to  a  place  oppo- 
site to  the  point  of  the  mucro  of  the  first  ventral  segment  of 
the  abdomen  will  appear.  In  Reaumur's  specimens,  these 
bundles  of  muscles  seem  to  have  been  cylindrical ;  but  in 
one  I  dissected  (Cicada  Capensis)  they  were  tubiform,  the 
end  to  which  the  true  drum  is  attached  being  dilated. 
These  bundles  consist  of  a  prodigious  number  of  muscular 
fibres  applied  to  each  other,  but  easily  separable.  Whilst 
Reaumur  was  examining  one  of  these,  pulling  it  from  its 
place  with  a  pin,  he  let  it  go  again,  and  immediately, 
though  the  animal  had  been  long  dead,  the  usual  sound 
was  emitted.  On  each  side  of  the  drum-cavities,  when 
the  opercula  are  removed,  another  cavity  of  a  lunulate 
shape,  opening  into  the  interior  of  the  abdomen,  is  ob- 
servable. In  this  is  the  true  drum,  the  principal  organ  of 


90  EVENINGS   AT    THE    MICEOSCOPE. 

sound,  and  its  aperture  is  to  the  Cicada  what  our  larynx  is 
to  us.  If  these  creatures  are  unable  themselves  to  modu- 
late their  sounds,  here  are  parts  enough  to  do  it  for  them : 
for  the  mirrors,  the  membranes,  and  the  central  portions, 
with  their  cavities,  all  assist  in  it.  In  the  cavity  last  de- 
scribed, if  you  remove  the  lateral  part  of  the  first  dorsal 
segment  of  the  abdomen,  you  will  discover  a  semi-opaque 
and  nearly  semicircular  concavo-convex  membrane  with 
transverse  folds  ;  this  is  the  drum.  Each  bundle  of  mus- 
cles, before  mentioned,  is  terminated  by  a  tendinous  plate, 
nearly  circular,  from  which  issue  several  little  tendons 
that,  forming  a  thread,  pass  through  an  aperture  in  the 
horny  piece  that  supports  the  drum  and  are  attached  to 
its  under  or  concave  surface.  Thus  the  bundle  of  muscles 
being  alternately  and  briskly  relaxed  and  contracted,  will 
by  its  play  draw  in  and  let  out  the  drum :  so  that  its  con- 
vex surface  being  thus  rendered  concave  when  pulled  in, 
when  let  out  a  sound  will  be  produced  by  the  effort  to  re- 
cover its  convexity ;  which,  striking  upon  the  mirror  and 
other  membranes  before  it  escapes  from  under  the  oper- 
culum,  will  be  modulated  and  augmented  by  them.  I 
should  imagine  that  the  muscular  bundles  are  extended 
and  contracted  by  the  alternate  approach  and  recession  of 
the  trunk  and  abdomen  to  and  from  each  other. 

"  And  now,  my  friend,"  adds  the  excellent  author, 
"  what  adorable  wisdom,  what  consummate  art  and  skill 
are  displayed  in  the  admirable  contrivance  and  complex 
structure  of  this  wonderful,  this  unparalleled  apparatus  ! 
The  great  Creator  has  placed  in  these  insects  an  organ  for 
producing  and  emitting  sounds  which  in  the  intricacy  of 
its  construction  seems  to  resemble  that  which  He  has 
given  to  man  and  the  larger  animals  for  receiving  them. 
Here  is  a  cochlea,  a  meatus,  and,  as  it  should  seem,  more 
than  one  tympanum !  " 

In  some  instances  the  sounds  of  insects  more  nearly 
approach  the  character  of  true  voices ;  at  least  so  far  as 


INSECTS  I    WINGS    AND   THEIB   APPENDAGES.  91 

they  are  produced  by  the  emission  of  air  from  the  breath- 
ing organs,  yet  not  by  means  of  the  mouth.  One  of  the 
most  eminent  of  continental  entomologists,  Dr.  Burmeister, 
tells  us  so.  Finding  that  the  buzz  of  a  large  fly  (Eristalis 
tenax)  still  continued  after  the  winglets,  the  poisers,  and 
even  the  wings,  had  been  quite  cut  off  except  their  stumps 
(only  in  this  last  case  the  sound  was  somewhat  weaker 
and  higher),  he  conceived  that  the  spiracles,  or  breathing 
holes,  lying  between  the  meso  and  meta-thorax  must  be  the 
instruments  of  the  sound ;  which,  accordingly,  he  found  to 
cease  entirely  when  they  were  stopped  with  gum,  though 
while  the  wings  were  in  vibration.  Pursuing  his  researches, 
he  extracted  one  of  these  spiracles,  and  opening  it  care- 
fully, found  its  posterior  and  inner  lip,  which  is  directed 
towards  the  commencement  of  the  trachea,  to  be  expanded 
into  a  small,  flat,  crescent-shaped  plate,  upon  which  are 
nine  parallel,  very  delicate,  horny  laminae,  the  central  one 
being  the  largest,  while  those  on  each  side  become  grad- 
ually smaller  and  lower ;  so  it  is,  he  is  persuaded,  in  con- 
sequence of  the  air  being  forcibly  driven  out  of  the  trachea 
and  touching  these  laminae  that  they  are  made  to  vibrate 
and  sound,  precisely  in  the  same  way  as  with  the  glottis  of 
the  larynx.  Dr.  Burmeister  (who  remarks  that  Chabrier, 
in  his  Essai  sur  le  Vol  des  Insectes,  p.  45,  &c.,  has  also 
explained  the  hum  of  insects  as  produced  by  the  air 
streaming  from  the  thorax  during  flight,  and  also  speaks  of 
laminae  which  lie  at  the  aperture  of  the  spiracles),  in  order 
to  be  certain  that  the  laminae  in  question  in  the  posterior 
spiracles  of  the  thorax  are  alone  concerned  in  producing 
sound,  also  inspected  the  anterior  ones,  but  without  find- 
ing in  them  any  trace  of  these  laminae.  He  explains  the 
weaker  and  sharper  tones  produced  when  the  wings,  all 
but  the  very  roots,  are  cut  off,  as  resulting  from  the  weaker 
vibrations  of  the  contracting  muscles,  and  consequently 
less  forcible  expulsion  of  the  air  when  the  vibratory  organs 
are  removed ;  and  he  thinks  with  Chabrier  that  some  air 


92  EVENINGS   AT    THE    MICROSCOPE. 

may  escape  through  the  open  trachea  of  the  wings  which 
are  cut  off.  Though  he  regards  these  laminas  as  the  cause 
of  humming  in  bees  and  flies,  he  does  not  decide  that  other 
causes  may  not  produce  the  buzz  of  cockchafers,  &c.,  in 
the  thoracic  spiracles  of  which  he  could  not  discern  them.* 

*  "  Man.  of  Entom,,"  468. 


INSECTS  :    THEIB   BBEATKLNG    OEGANS.  93 


CHAPTER  VI. 

INSECTS  I    THEIB   BREATHING   ORGANS. 

IN  order  to  understand  the  passage  last  quoted  from  Bur- 
meister,  you  ought  to  know  something  of  the  manner  in 
•which  breathing  is  performed  among  insects.  Essentially, 
breathing  is  the  same  function,  wherever  it  occurs ;  and 
it  does  occur,  doubtless,  in  all  animals  under  some  form 
or  other.  It  is  the  absorption  of  oxygen  from  without  to 
the  fluids  within,  to  repair  the  waste  constantly  produced 
by  vital  energy.  But  it  may  be  obtained  from  different 
sources,  and  imbibed  in  various  modes. 

All  insects  in  the  perfect  state  are  air-breathers ;  that 
is,  they  procure  their  oxygen  from  the  air  as  we  do  ;  and 
most  of  them  are  such  in  their  earlier  stages.  Even  in 
exceptional  cases,  viz.,  those  larvae  or  pupae  which  are  pro- 
vided with  what  represent  gills,  and  appear  to  be  de- 
pendent on  the  water  for  their  respiration,  the  exception  is 
rather  apparent  than  real,  for  the  function  is  still  per- 
formed in  air-vessels.  Now  these  air-vessels  shall  afford 
us  some  interesting  microscopical  observations. 

This  brown  fly,  which  is  buzzing  and  hovering  on 
invisible  wings  over  the  flowers  in  the  garden,  you  perhaps 
take  for  a  bee.  No  ;  it  has  but  two  wings ;  for  I  have 
caught  it,  and  you  may  ascertain  the  fact  for  yourself ;  it 
belongs  to  the  genus  Syrphus.  Having  caught  it,  I 
deprive  it  of  life  by  means  of  the  very  organs  I  am  going 
to  examine,  for  I  turn  a  tumbler  over  it  and  insert  under 
the  edge  a  lighted  lucifer-match.  In  a  few  seconds  it  is 
dead — suffocated ;  for  phosphoric  and  sulphuric  acids  in- 


94  EVENINGS  AT  THE  MICROSCOPE. 

troduced  into  the  breathing  tubes  quickly  destroy  life.  I 
presently  take  it  out,  and,  putting  it  into  a  dissecting- 
trough  under  a  lens,  cut  up  the  abdomen  with  a  pair  of 
fine-pointed  scissors.  Then  I  pin  open  the  divided  abdo- 
men to  the  bottom  of  the  trough,  which  is  coated  with 
wax  for  the  purpose ;  and,  looking  at  it  with  the  lens — 
but  you  shall  look  for  yourself. 

Well,  you  see  little  else  but  the  polished  brown  walls  of 
the  body  and  a  number  of  fine  white  threads.  It  is  those 
threads  that  we  want.  With  a  small  camel' s-hair  pencil 
I  move  them  to  and  fro  in  the  water,  and  soon  perceive 
that  they  are  like  little  trees  with  comparatively  thick 
trunks,  sending  off  many  branches,  and  gradually  be- 
coming exceedingly  slender.  Here  and  there  short  thick 
branches  break  out  on  two  opposite  sides,  and  on  each 
side  are  connected  with  the  wall  of  the  abdomen.  Here 
then  with  the  fine  scissors  I  snip  them  across,  and  lift  up 
a  portion  with  the  hair  pencil  into  a  drop  of  water  which 
I  have  already  put  into  the  live  box.  The  cover  now 
flattens  the  drop,  spreads  the  white  threads, — and  the 
object  is  ready  for  our  eye. 

We  have  before  us  a  considerable  portion  of  the  tra- 
cheal  system  of  the  fly.  And  though,  owing  to  the  com- 
plication of  the  parts  and  the  injury  our  rude  anatomy 
has  done,  we  cannot  trace  the  beautiful  regularity  which 
exists  in  life,  we  may  see  the  principle  on  which  they  are 
arranged,  and  much  of  the  perfection  with  which  they  are 
constructed. 

Here  then  is  a  system  of  pipes, — some  large,  some 
small ;  the  smaller  branching  forth  from  the  large,  and 
themselves  sending  off  yet  smaller  branches,  which  in 
their  turn  divide  and  subdivide  until  the  final  ramifications 
are  excessively  attenuated.  Besides  these,  we  see  here 
and  there  ovate  or  barrel-shaped  reservoirs,  having  the 
same  appearance  and  intimate  structure  as  the  pipes,  but 
of  much  larger  calibre  and  connected  with  them  by  a  branch. 


INSECTS  :    THEIR   BREATHING    ORGANS.  95 

This,  I  say,  is  the  breathing  system,  or  a  large  portion 
of  it.  These  pipes  receive  the  air  from  without  through 
trap- doors  which  we  will  examine  presently,  and  convey  it 
to  the  most  distant  parts  of  the  body.  In  ourselves  the 
air  is  inhaled  into  a  great  central  reservoir — the  lungs — 
and  the  blood  dispersed  through  every  part  is  brought  to 
this  reservoir  to  be  oxygenated.  In  insects  it  is  the  blood 
that  is  collected  into  a  great  central  reservoir,  and  the  air 
is  distributed  by  a  minutely  divided  system  of  vessels  over 
the  blood-reservoir. 

The  trachea  or  air-pipes  have  a  silvery  white  appear- 


AIE-PIPE  OF  FLY. 


ance  by  reflected  light;  but  if  we  use  transmitted  light 
and  put  on  a  high  power,  we  discern  a  wonderful  struc- 
ture, which  I  will  describe  in  the  eloquent  language  of 
Professor  Bymer  Jones,  and  you  shall  estimate  its  truth  as 
you  examine  the  object : — 

* '  There  is  one  elegant  arrangement  connected  with  the 
breathing-tubes  of  an  insect  specially  worthy  of  admira- 
tion ;  and  perhaps  in  the  whole  range  of  animal  mechanics 
it  would  be  difficult  to  point  out  an  example  of  more 
exquisite  mechanism,  whether  we  consider  the  object  of 


96  EVENINGS   AT    THE    MICROSCOPE. 

the  contrivance  or  the  remarkable  beauty  of  the  structure 
employed.  The  air-tubes  themselves  are  necessarily  ex- 
tremely thin  and  delicate ;  so  that  on  the  slightest  pres- 
sure their  sides  would  inevitably  collapse  and  thus  com- 
pletely put  a  stop  to  the  passage  of  air  through  them, 
producing,  of  course,  the  speedy  suffocation  of  the  insect, 
had  not  some  means  been  adopted  to  keep  them  always 
permeable  ;  and  yet  to  do  so,  and  at  the  same  time  to 
preserve  their  softness  and  perfect  flexibility,  might  seem 
a  problem  not  easily  solved.  The  plan  adopted,  however, 
fully  combines  both  these  requisites.  Between  the  two 
thin  layers  of  membrane  which  form  the  walls  of  every  air- 
tube,  a  delicate  elastic  thread  (a  wire  of  exquisite  tenuity) 
has  been  interposed,  which,  winding  round  and  round  in 
close  spirals,  forms  by  its  revolutions  a  cylindrical  pipe  of 
sufficient  firmness  to  preserve  the  air-vessels  in  a  per- 
meable condition,  whilst  at  the  same  time  it  does  not  at 
all  interfere  with  its  flexibility ;  this  fine  coil  is  continued 
through  every  division  of  the  trachea,  even  to  their  most 
minute  ramifications,  a  character  whereby  these  vessels 
are  readily  distinguishable  when  examined  under  the 
microscope."  * 

Man  has  imitated  this  exquisite  contrivance  in  the 
spiral  wire-spring  which  lines  flexible  gas-pipes ;  but  his 
wire  does  not  pass  between  two  coats  of  membrane.  One 
of  the  most  interesting  points  of  the  contrivance  is  the 
way  in  which  the  branches  are  (so  to  speak)  inserted 
in  the  trunk,  the  two  wires  uniting  without  leaving  a 
blank.  It  is  difficult  to  describe  how  this  is  done  ;  but 
by  tracing  home  one  of  the  ramifications  you  may  see 
that  it  is  performed  most  accurately ;  the  circumvo- 
lutions of  the  trunk-wire  being  crowded  and  bent  round 
above  and  below  the  insertion  (like  the  grain  of  timber 
around  a  knot),  and  the  lowest  turns  of  the  branch- wire 
being  enlarged  so  as  to  fill  up  the  opening  entirely. 
*  "  Nat.  Hist,  of  Anim.,"  i.  6. 


INSECTS  :    THEIE    BEEATHING    ORGANS.  97 

You  must  not  suppose,  however,  that  the  whole  of  one 
tube  is  formed  out  of  a  single  wire.  Just  as  in  a  piece  of 
human  wire-work  the  structure  is  made  out  of  a  certain 
number  of  pieces  of  limited  length,  and  joinings  or  inter- 
lacings  occur  where  new  lengths  are  introduced,  so, 
strange  to  say,  it  seems  to  be  here.  It  is  strange,  I  say, 
that  it  should  be  so,  when  there  can  be  no  limit  to  the 
resources,  either  of  material,  or  skill  to  use  it ;  but  so  it 
is,  as  you  may  see  in  this  specimen,  which  has  been  dis- 
sected out  of  the  body  of  a  silkworm.  The  spiral  is 
much  looser  here  than  in  the  air-tube  of  the  fly,  the  turns 
of  the  wire  being  wider  apart ;  and  hence  its  structure  is 
much  more  easily  traced.  Here  you  see  in  many  places 
the  introduction  of  a  new  wire,  always  commencing  with 
the  most  fine-drawn  point,  but  presently  taking  its  place 
with  the  rest  so  as  to  be  undistinguishable  from  them. 
In  some  cases  certainly  (perhaps  this  may  be  the  expla- 
nation of  the  phenomenon  in  all)  the  wire  so  introduced 
may  be  found  to  terminate  with  the  like  attenuation  before 
it  has  made  a  single  turn,  and  seems  to  be  inserted  when 
the  permanent  curvature  of  the  pipe  would  leave  the  wires 
on  the  outer  side  of  the  curve  too  far  apart,  half  a  turn, 
or  even  much  less,  then  being  inserted  of  supernumerary 
wire. 

I  told  you  that  the  air  enters  these  tubes  through  cer- 
tain "  trap- doors."  This  is  not  the  term  which  the 
physiologist  employs,  certainly :  he  calls  them  spiracles. 
In  our  own  bodies  the  air  enters  only  at  one  spiracle, 
a  curiously  defended  orifice  opening  just  in  front  of  the 
gullet,  at  the  back  of  the  mouth.  But  in  the  class  of 
animals  we  are  now  considering  there  are  a  good  many 
such  breathing  orifices.  You  may  see  them  to  great 
advantage  in  any  large  caterpillar,  the  silkworm  for 
example,  where  all  along  the  sides  of  the  pearl-grey  body 
you  perceive  a  row  of  dots,  which  with  a  lens  you  dis- 
cover to  be  little  oval  disks  sunken  into  little  pits,  of 

H 


98 


EVENINGS    AT    THE    MICROSCOPE. 


a  black  hue  with  a  white  centre,  through  which  is  a  very 
slender  slit.  There  are  nine  of  these  organs  on  each  side, 
a  pair  to  each  segment  or  division  of  the  body,  with  the 
exception  of  the  first,  which  is  the  head,  and  of  the  third 
and  fourth,  which  are  destined  to  bear  the  wings ;  these 
are  destitute  of  spiracles. 

Essentially,  these  organs,  under  whatever  modifications 
of  form  and  position  they  may  appear,  have  the  same 
structure.  They  are  narrow  orifices,' with  two  lips  capable 
of  being  opened  at  the  will  of  the  animal,  or  accurately 
closed;  and  in  many  soft-skinned  insects,  such  as  the 
silkworm,  and  most  lame,  they  are  set  in  a  horny  ring, 
by  which  means  they  are  prevented  from  collapsing, 
through  the  unresisting  character  of  the  general  integu- 
ment. The  opening  and  shutting  of  them  is  performed  by 
an  internal  apparatus  of  muscles,  which  is  sometimes 
strengthened  by  being  attached  to  two  horny  plates,  which 
project  inwardly. 

But  the  most  curious  thing 
to  be  noted  in  the  structure 
of  these  spiracles  is  the  con- 
trivance which  induced  me 
to  call  them  trap  -  doors. 
Small  as  are  their  openings, 
they  are  still  large  enough 
to  admit  many  floating  par- 
ticles of  dust,  soot,  and 
other  extraneous  matters, 
which  would  tend  to  clog 
up  the  delicate  air-passages, 
and  to  impede  the  right 
performance  of  their  im- 
portant functions.  Hence 
they  need  to  be  guarded 
with  some  sort  of  sieve,  or 
filter,  which,  while  admitting  the  air,  shall  exclude  the  dust. 


SPIRACLE    OF    FLY. 


INSECTS :    THEIK    BREATHING    ORGANS. 


99 


Various  and  beautiful  are  the  modes  in  which  this 
common  purpose  is  effected,  but  I  can  show  you  only  two 
or  three.  This  is  one  of  the  breathing  orifices  of  the 
common  House-fly,  in  which,  as  you  see,  minute  processes 
grow  from  the  margin  all  round,  which  extend  partly  across 
the  open  area,  branching  and  ramifying  again  and  again, 
and  spreading  and  interlacing  with  those  of  the  opposite 
side,  so  as  to  form  a  perfect  sieve,  which  the  finest  atoms 
of  dust  cannot  penetrate. 

The  same  end  is  attained,  in  another  way,  in  the  dirty 
cylindrical  grub,  which  is  found  so  abundantly  at  the  roots 
of  .grass  in  pasture  lands,  and  which  country  folk  call, 
from  the  toughness  of  its  skin,  "  leather-coat."  It  is  the 
larva  of  the  Crane-fly  (Tipula  oltracea),  so  familiar  to  us 
under  the  sobriquet  of  Daddy  Long-legs.  I  can  easily 
procure  one  of  these,  for,  unfortunately,  they  are  but  too 
common.  Here  is  one,  who  shall  have  the  honour  of  being 
martyred  for  the  benefit  of  science.  Before  we  assassinate 
him,  however,  just  look  here  at  the  hinder  extremity  of  his 
body,  where  there  is  a  space, 
surrounded  and  protected  by 
several  points,  and  in  this 
space,  two  black  spots. 

With  the  dissecting-scissors 
I  have  carefully  cut  out  one 
of  these  specks,  and  now  I  put 
it  for  illumination  on  the  stage 
of  the  microscope.  There  is, 
first  of  all,  a  dark  homy  ring 
of  an  oval  figure,  a  little  way 
within  which  there  is  an 
opaque  dark  plate  of  the  same 
figure,  but  smaller,  occupying 
the  central  portion  of  the  area, 
margin  of  the  plate  and  the  bounding  ring  is  occupied  by 
a  series  of  slender  filaments,  placed  side  by  side,  proceed- 
H  2 


BPIKACLE   OF   LXATHKR-COAT. 


The  space  between  the 


100 


EVENINGS    AT    THE    MICROSCOPE. 


ing  from  one  to  the  other,  through  the  interstices  of  which 
the  air  is  filtered.  The  central  plate  seems  to  be  quite 
imperforate. 

The  fat,  thick-bodied  grubs  of  those  beetles  called 
chafers  exhibit,  in  their  spiracles,  a  modification  of  this 
structure,  rendered  still  more  elaborate.  In  the  case  of 

the  larva  of  the  common 
Cockchafer  (Melolontha  vul- 
garis),  for  example,  the  cen- 
tral plate  is  a  projection 
from  one  side  of  the  margin 
of  the  spiracle  ;  or,  to  use  a 
geographical  simile,  we  may 
say  that,  instead  of  being 
an  island  in  the  midst  of  a 
lake,  it  is  a  promontory. 

Thus  the  breathing  space 
is  a  crescent-shaped  band, 
which  is  crossed  in  every 
part  by  bars  passing  from 

the  margin  to  the  projecting  plate.  But,  as  if  the  inter- 
stices left  by  these  bars  would  be  too  coarse  for  the  pur- 
pose, they  are  made  still  finer  by  a  membrane,  which  is 
stretched  across  them,  and  which  is  pierced  with  a  number 
of  exceedingly  minute  round  holes,  through  which  alone 
the  air  is  admitted. 

In  many  of  the  two-winged  flies,  which  inhabit  the 
water  in  their  earlier  stages,  there  are  some  interesting 
contrivances  and  modifications  connected  with  the  organs 
of  respiration.  It  is  necessary  that  the  orifices  of  the 
air-tubes  should  be  brought  at  intervals  to  the  surface  of 
the  water,  in  order  to  come  into  contact  with  the  external 
air  ;  while,  at  the  same  time,  it  is  important  that  as  small 
a  portion  as  possible  of  the  animal's  body  be  exposed  to 
danger,  by  being  protruded  from  its  sheltering  element. 
An  example  in  point  you  may  see  in  this  vase. 


SPIRACLE  OF  COCKCHAFER-GRUB. 


INSECTS  I    THEIR    BREATHING    ORGANS.  101 

Here  is  a  slender  worm,  an  inch  and  a-half  in  length, 
thickest  a  little  behind  the  head,  and  tapering  gradually  to 
a  lengthened  tail,  the  twelve  divisions  of  the  body  being 
very  conspicuous.  It  swims  up  and  down  or  to  and  fro 
in  the  clear  water  with  a  not  very  rapid,  wriggling  move- 
ment, throwing  its  body  alternately  from  side  to  side  in 
the  form  of  the  letter  S. 

This  is  the  maggot  of  a  handsome  dipterous  fly,  some- 
times called  the  Chameleon-fly  (Stratiomys  chameleon). 
There  is  much  about  it  to  reward  observation  and  careful 
examination  with  a  low  magnifying  power,  especially  the 
head,  with  its  pointed  snout,  and  its  pair  of  foot-like 
palpi,  or  feelers.  These  are  situated  one  on  each  side  of 
the  head,  are  three-jointed,  the  last  joint  being  studded 
with  short  stiff  spines,  and  the  second  having  a  thumb - 
like  projection.  With  these  organs,  the  grub  roots  and 
burrows  among  the  decaying  vegetable  matter  at  the 
bottom  for  its  food  ;  and  when  not  so  engaged,  they  are 
often  rapidly  vibrated  in  a  singular  manner,  the  sight  of 
which  might  induce  a  feeling  of  fear,  as  if  they  were 
threatening  weapons  of  offence — a  pair  of  poisonous  stings, 
for  instance  ;  they  have,  however,  no  such  function,  the 
poor  grab  being  perfectly  harmless. 

What  I  wish  you  chiefly  to  observe,  however,  is  the 
tail,  with  its  curious  organisation.  With  the  naked  eye, 
you  can  perceive  that  the  last  joint  is  much  slenderer 
and  more  lengthened  than  the  rest,  and  that  it  is  tipped 
with  a  beautiful  crown  of  feathers,  like  the  diadem  of 
some  semi-savage  prince.  This  is  best  seen  when*  the 
animal  comes  to  the  surface,  which  it  always  does  tail 
uppermost ;  for,  as  soon  as  the  tip  reaches  the  air,  the 
plumes  instantly  open,  and  form  an  exquisite  cone  or 
funnel,  from  which  every  drop  of  moisture  is  excluded, 
though  the  water  stands  around  at  the  level  of  the  brim. 
A  few  seconds  it  remains  motionless  thus,  the  whole  body 
hanging  downwards,  suspended  from  the  caudal  coronet, 


102 


EVENINGS    AT    THE    MICEOSCOPE. 


then  suddenly  the  tips  of  the  plumes  curve  inward  toward 
each  other,  inclosing  a  globule  of  air,  and  the  animal 
wriggles  away  into  the  depths,  carrying  its  burden,  like  a 
pearl,  or  a  glittering  bubble  of  quicksilver,  behind  it. 

This  you  may  observe  with  the  unassisted  sight ;  and 
you  may  mark  also,  how,  from  time  to  time,  a  portion, 
more  or  less,  of  the  bubble  of  gleaming  air  is  inhaled  or 
expired  by  the  animal,  causing  a  diminution  or  increase 
of  its  volume ;  and  this  of  itself  would  convince  you  that 
it  is  the  spiracles  of  the  animal  which  are  thus  pro- 
tected. 

The  application  of  a 
low  magnifying  power, 
say  from  thirty-five  to 
fifty  diameters,  for  we 
can  hardly  use  a  higher 
power  than  this  to  the 
animal  while  alive,  will 
reveal  a  few  more  of  the 
details. 

We  see,  then,  that  the 
extremity  of  the  last  seg- 
ment forms  a  circular 
disk,  hollowed  in  the 
centre,  where  it  is  per- 
forated with  the  two 
orifices  of  the  air-pipes. 
The  margin  of  this  disk 
carries  about  thirty  stiff 
but  slender  spines  or 
bristles,  some  of  which 
are  branched  in  a  forked 
manner.  Each  bristle 
bears,  on  its  two  oppo- 
site sides — viz.,  on  those 
aspects  which  face  the  next  bristle  on  either  hand— two 


GIIUB  OF  CHAMELEON-FLY. 


INSECTS  I    THEIR    BREATHING    ORGANS.  103 

series  of  not  very  close-set  branchlets,  set  like  the  plumes 
of  a  feather,  or  the  pinnse  of  a  fern-leaf,  which  give  it 
the  elegant  plumose  appearance  which  the  unassisted  eye 
recognises.  The  bristles  have  a  granulose  surface  near 
the  extremity,  and  terminate  in  fine  points. 

The  curious  faculty  of  repelling  water,  which  the  in- 
terior surface  of  this  plumy  coronet  possesses,  is  of  the 
highest  value  in  the  economy  of  the  insect ;  for,  on  the 
one  hand,  it  permits  the  breathing  orifice  to  be  brought 
into  contact  with  the  air,  even  when  nearly  a  quarter  of 
an  inch  below  the  surface  ;  and  on  the  other  hand,  it 
allows  the  volume  of  air  inclosed  within  the  funnel  to 
be  perfectly  isolated  and  carried  securely  away,  as  a 
reservoir  for  the  wants  of  the  animal,  when  engaged  in 
its  avocations  of  necessity  or  pleasure,  in  the  recesses  of 
its  sub- aquatic  groves.  It  is  remarkable  that  so  com- 
plete is  this  repellent  power,  that  when  the  tail  is  at  the 
surface  the  animal  may  make  a  very  perceptible  descent 
without  breaking  the  continuity  of  the  air,  the  surface 
presenting  the  curious  phenomenon  of  a  deep  funnel- 
shaped  dimple  leading  down  to  the  tail. 

The  chameleon-fly  is  not,  however,  so  abundant  and 
so  universally  distributed  as  that  you  may  always  calculate 
upon  being  able  to  repeat  these  observations  when  you 
will.  I  shall,  therefore,  show  you  an  analogous  example, 
much  more  easily  obtained.  Both  are  inhabitants  of  our 
fresh  waters  :  the  chameleon-grub  lives  in  ponds,  crawling 
among  the  stems  of  aquatic  plants,  and  occasionally  visit- 
ing the  surface  in  the  manner  you  have  seen ;  but  it  is 
uncertain,  in  some  seasons  not  uncommon,  in  others, 
scarcely  to  be  met  with  by  the  most  persevering  search. 
For  my  next  specimen,  I  have  but  to  go  with  a  basin  to  the 
water-butt  in  the  yard,  and  take  a  dip  of  the  surface-water 
at  random :  I  shall  be  pretty  sure  of  a  score  at  least. 

Here  they  are  swarming,  as  I  told  you.  What,  those 
things  ?  why,  they  are  gnat-grubs.  Well,  don't  despise 


104  EVENINGS   AT    THE    MICBOSCOPE. 

them,  you  will  find  them  worth  looking  at.  I  dare  say 
you  have  never  submitted  them  to  half-an-hour's  micro- 
scopical examination.  I  have  caught  one  with  a  spoon, 
and  put  it  into  this  narrow  glass  trough  of  water  that  it 
may  rest  conveniently  on  the  stage. 

We  will  take  a  cursory  glance  at  its  entire  person. 
Here  is  a  flat,  roundish  head,  a  great  globose,  swollen 
thorax,  and  a  long,  slender,  many-jointed  body,  ending  in 
a  curious  fork.  But  all  is  curious : — the  head,  with  its 
horny  transparency ;  its  pair  of  rod-like  antenna,  covered 
with  minute  points ;  its  two  black  eye -patches  ;  and  its 
jaws,  beset  with  strong,  curved  hairs,  set  in  radiating 
rows,  and,  ever  and  anon,  working  to  and  fro  with  the 
most  rapid  vibrations :  the  thorax, — so  transparent,  with 
its  amber-like  clearness,  that  you  can  discern  the  dorsal 
vessel,  which  contains  the  blood,  ever  dilating  and  col- 
lapsing with  the  most  beautiful  regularity ;  and  beneath 
this,  the  gullet,  through  which,  now  and  then,  descends  a 
dark  pellet  of  food,  to  join  the  mass  already  lodged  in 
the  stomach  farther  down, — a  result,  by  the  way,  that 
explains  that  incessant  vibration  and  pumping  motion  of 
the  mouth-organs,  which  thus  evidently  are  engaged  in 
collecting  food  from  the  water;  though,  even  with  this 
power,  we  can  see  no  solid  matter  taken  in,  till  we  dis- 
cern it  agglomerated  in  the  swallowed  pellets  :  the  body, 
or  abdomen,  with  its  ten  joints,  all  (with  a  slight  excep- 
tion) the  counterparts  of  each  other ;  and  each  carrying 
its  own  dilatation  of  the  dorsal  vessel,  and  its  own  portion 
of  the  long  and  well-filled  intestinal  canal.  All  these, 
I  say,  are  very  interesting  and  curious  to  observe ;  espe- 
cially when  we  select,  as  I  have  done,  a  young  indi- 
vidual for  examination ;  since  the  tissues  then  possess  a 
translucency  which  is  essential  to  our  seeing  with  dis- 
tinctness anything  of  the  internal  organisation,  but 
which  soon  gives  place  to  opacity,  as  the  insect  advances 
in  age. 


INSECTS:  THEIR  BREATHING  ORGANS.  105 

Very  curious,  too,  are  the  hairs  with  which  the  whole 
surface  of  the  animal  is  furnished  at  certain  definite 
points.  But  these  are  seen  to  more  advantage  in  an 
older  specimen ;  for,  in  this  one  of  tender  hours,  they  are 
nearly  simple ;  whereas,  in  an  opaque,  nearly  full-grown 
individual,  every  hair  is  seen  to  be  studded  with  second- 
ary points,  that  project  from  its  surface  throughout  its 
length.  These  hairs  are  arranged  in  beautiful  radiating 
pencils  or  tufts,  and  scattered,  as  I  have  said,  at  definite 
points  over  the  whole  body  ; — there  is  a  tuft  on  each 
antennae ;  one  on  the  forehead  ;  one  in  front  of  each  eye- 
spot  ;  several  circles  of  them  set  round  the  thorax ;  one 
circle  of  scanty  pencils  set  round  each  segment  of  the 
body,  and  a  few  smaller  tufts  scattered  about  besides  ;  all 
of  them  springing  from  minute  round  warts. 

The  extremity  of  the  abdomen  deserves,  however,  a 
separate  investigation,  and  we  will  now  direct  our  atten- 
tion to  the  tail-end  of  our  tiny  grub.  There  are  ten 
segments  to  the  abdomen ;  at  the  eighth  it  seems  to 
divide  into  two  branches,  one  longer  than  the  other. 
This  appearance,  however,  is  due  to  the  circumstance  that 
the  respiratory  tube  is  sent  forth  from  the  eighth  segment, 
and  that  the  ninth  and  tenth  segments  are  bent  away  at 
an  angle  from  the  general  line  of  the  body. 

The  ninth  segment  is  very  small :  the  tenth  is  squarish, 
with  rounded  corners,  and  is  brought  to  a  thin  edge. 
Around  the  margin  there  is  the  most  exquisite  array  of 
hairs  possible ;  at  one  corner  there  are  three  pencils  ; 
while  round  the  opposite  and  down  the  corresponding  side 
run,  in  two  rows,  twelve  pencils  set  very  close  to  each 
other,  and  each  containing  a  large  number  of  very  slender 
hairs.  The  extreme  end  of  the  segment  is  ornamented 
with  four  diverging  organs  of  taper  conical  form  and 
crystalline  clearness,  through  the  midst  of  each  of  which 
passes  a  very  fine  branch  of  the  air- tube  system,  which 
gives  off  still  more  attenuated  branchlets  in  its  course. 


106  EVENINGS   AT    THE    MICROSCOPE. 

We  have  not  yet,  however,  examined  the  origin  of  this 
air-breathing  system.  There  is  but  one  entrance  to  the 
air,  or  rather  two  placed  close  together,  at  the  end  of 
that  round  column,  which  is  sent  off  from  the  eighth 
segment  of  the  abdomen.  This  column,  which  is  rough- 
ened all  over  with  minute  points,  and  fringed  with  rows  of 
hairs,  ends  in  a  horny,  conical  point,  which  seems  entire 
while  under  water,  but  no  sooner  does  it  come  to  the  sur- 
face, than  it  is  seen  to  split  into  five  triangular  pieces, 
which  open  widely,  and  expose  a  hollow,  at  the  bottom  of 
which  are  the  two  spiracles. 

From  these  the  two  main  air-pipes  are  seen  to  com- 
mence, and  to  proceed  along  the  centre  of  the  column, 
thence  into  the  abdomen,  which  they  traverse  one  along 
each  side,  sending  off  slender  branchlets  all  along,  and 
becoming  more  and  more  attenuated  themselves ;  till,  at 
length,  we  trace  them  into  the  thorax,  and  thence  through 
the  slender  neck  into  the  head  itself,  until  they  terminate 
in  fine  points  close  to  the  back  of  the  mouth.  It  needs, 
it  is  true,  a  very  transparent  specimen  to  follow  the 
tracheal  tubes  thus  through  their  entire  course;  but  in 
such  it  can  be  done  without  difficulty.  And  it  is  very 
instructive  to  do  so,  inasmuch  as  one  such  personal 
examination  of  an  insect  under  a  good  microscope  will 
make  you  far  more  familiar  with  the  peculiarities  of  its 
physiology  than  the  clearest  book- descriptions,  or  even 
the  best  and  most  elaborate  plates,  alone. 

Perhaps  you  may  think  I  have  kept  you  too  long  over 
these  gnat-grubs,  but  my  reason  for  being  more  minute 
in  the  examination  of  this  creature  is,  that  its  extreme 
abundance  in  every  place,  and  through  the  greatest  part 
of  the  year,  puts  it  in  the  power  of  every  one  to  procure 
a  specimen  alive  and  healthy  almost  whenever  he  chooses  ; 
and,  therefore,  it  is  peculiarly  available  for  microscopic 
study  ;  while  the  transparency  of  its  tissues,  and  its  gene- 
rally simple  organisation,  make  it  a  more  than  usually 


INSECTS  :    THEIB    BBEATHING    ORGANS.  107 

suitable  object  for  investigation ;  besides  which,  there 
are  the  beautiful  and  interesting  points  in  the  details  of 
its  structure  which  I  have  been  endeavouring  to  bring 
before  you. 

Not  less  interesting  and  remarkable  is  the  change  in 
the  position  of  the  spiracles,  which  takes  place  as  soon  as 
this  grub  arrives  at  the  pupa  or  chrysalis  state.  The  skin 
of  the  active,  fish-like  larva  splits  down  the  back,  and  out 
presses  an  equally  active  little  monster ;  which,  if  you  did 
not  know  it,  you  would  never  think  of  connecting  with  the 
grub  from  which  it  has  proceeded  ;  so  totally  different  is 
it  in  form,  in  structure,  and  in  motions. 

We  shall  easily  find  some  in  our  basin  that  have  passed 
into  this  stage.  Yes,  here  is  one,  which  will  please  to 
take  its  place  in  the  glass  trough  with  its  younger  brothers. 
How  strange  the  transformation  !  It  reminds  us  of  a 
lobster,  though,  of  course,  the  resemblance  is  only  appa- 
rent. With  the  naked  eye  we  see  that  the  thorax  is 
greatly  enlarged,  not  only  actually,  but  proportionally ; 
that  it  forms  an  oval  mass,  occupying  some  five- sixths,  at 
least,  of  the  entire  animal ;  the  rest  apparently  being 
taken  up  by  a  slender,  many-jointed  abdomen,  which 
curves  round  the  great  thorax,  and,  bending  under  it,  ends 
in  a  very  delicate,  transparent  swimming-plate.  It  is 
this  curving  abdomen,  with  its  terminal  swimmer,  and  its 
backward  strokes  in  swimming,  that  constitute  the  resem- 
blance to  a  prawn  or  lobster. 

If  we  now  bring  a  low  power  with  reflected  light  to  bear 
on  it,  we  shall  see  the  progress  the  animal  has  made  in 
this  its  change  of  raiment.  The  thorax  shows  on  its 
sides  the  future  wings,  crumpled  and  folded  down,  the 
nervures  of  which  we  can  discern  distinctly.  The  elegant 
little  head,  too,  can  be  well  made  out ;  its  eyes  now  per- 
fectly marked  with  the  numerous  six-sided  facets  that 
belong  to  the  matured  organs  of  vision  in  these  creatures  ; 
its  antennae,  like  slender  rods,  folded  down  side  by  side 


108  EVENINGS    AT    THE    MICROSCOPE. 

along  the  inferior  edge  of  the  thorax ;  the  short  palpi 
lying  outside  these  ;  and  within,  both  the  lancets  and 
piercers  that  are  destined  to  subserve  the  blood-sucking 
propensities  of  our  sanguinary  little  subject,  when  it 
attains  its  winged  condition ; — all  encased  in  the  trans- 
parent pupa-skin,  that  lies  like  a  loose  wrapper  around 
everything. 

The  extremity  of  the  abdomen  has  now  nothing  to  do 
with  respiration,  and  hence  it  is  never  brought  to  the 
surface  of  the  water,  as  it  was  constantly  before.  The 
little  animal  still  habitually  lives  in  contact  with  the  air, 
coming  up  to  it  with  rapid,  impatient  jerks,  whenever  it 
has  descended;  but  it  is  invariably  the  summit  of  the 
thorax  that  is  uppermost,  and  when  the  creature  rests,  it 
is  this  part  that  touches  the  surface. 

Why  is  this  ?  you  ask.  Look,  and  you  will  see  why. 
From  the  summit  of  the  thorax  project  two  little  horns, 
which,  under  the  microscope,  are  seen  to  be  clear  trum- 
pet-shaped tubes  with  open  mouths,  cut  as  it  were 
obliquely  off.  These  enter  the  thorax  close  to  the  bases 
of  the  wings  ;  and  when  we  confine  the  animal  in  a  glass 
cell,  exercising  a  gentle  pressure  upon  the  thorax,  we  see 
bubbles  of  air  alternately  projected  from  the  trumpet 
mouths  of  the  tubes  and  sucked  in  again.  These,  then, 
are  the  spiracles,  the  orifices  of  the  air-tubes,  where  the 
vital  fluid  enters  the  body,  and  whence  it  is  carried  to 
every  part  of  the  system. 

There  is  something  curiously  beautiful  about  the  struc- 
ture of  these  spiracular  tubes,  of  which  I  cannot  attempt 
to  explain  the  object.  With  a  high  magnifying  power, 
their  whole  exterior  surface  is  seen  to  be  covered  with 
regular  rounded  scales,  overlapping  each  other,  and  very 
closely  resembling  those  of  a  fish. 


INSECTS  I     THEIB    FEET.  109 


CHAPTER  VII. 

INSECTS  I    THEIR    FEET. 

I  HAVE  here  inclosed  a  small  window-fly  in  the  live -box  of 
the  microscope,  that  you  may  examine  the  structure  of  its 
feet  as  it  presses  them  against  the  glass  cover  ;  and  thus 
not  only  get  a  glimpse  of  an  exquisitely-formed  structure, 
but  acquire  some  correct  ideas  on  the  question  of  how  a 
fly  is  enabled  to  defy  all  the  laws  of  physics,  and  to  walk 
jauntily  about  on  the  under  surface  of  polished  bodies, 
such  as  glass,  without  falling,  or  apparently  the  fear  of 
falling.  And  a  personal  examination  is  the  more  desirable 
because  of  the  hasty  and  erroneous  notions  that  have  been 
promulgated  on  the  matter,  and  that  are  constantly  dis- 
seminated by  a  herd  of  popular  compilers,  who  profess  to 
teach  science  by  gathering  up  and  retailing  the  opinions 
of  others,  often  without  the  slightest  knowledge  whether 
what  they  are  reporting  is  true  or  false. 

The  customary  explanation  has  been  that  given  by  Der- 
ham  in  his  "  Physico- theology  "  ;  that  "  divers  flies  and 
other  insects,  besides  their  sharp-hooked  nails,  have  also 
skinny  palms  to  their  feet,  to  enable  them  to  stick  to  glass, 
and  other  smooth  bodies,  by  means  of  the  pressure  of  the 
atmosphere,  after  the  manner  as  I  have  seen  boys  carry 
heavy  stones,  with  only  a  wet  piece  of  leather  clapped  on 
the  top  of  a  stone."  Bingley,  citing  this  opinion,  adds 
that  they  are  able  easily  to  overcome  the  pressure  of  the 
air  "in  warm  weather,  when  they  are  brisk  and  alert; 
but  towards  the  end  of  the  year  this  resistance  becomes 
too  mighty  for  their  diminished  strength ;  and  we  see  flies 


110  EVENINGS    AT    THE    MICROSCOPE. 

labouring  along,  and  lugging  their  feet  on  windows  as  if 
they  stuck  fast  to  the  glass  :  and  it  is  with  the  utmost 
difficulty  they  can  draw  one  foot  after  another,  and  dis- 
engage their  hollow  cups  from  the  slippery  surface."* 

But  long  ago  another  solution  was  proposed  :  for  Hooke, 
one  of  the  earliest  of  microscopic  observers,  described  the 
two  palms,  pattens,  or  soles  (as  he  calls  the  pulvilli),  as 
11  beset  underneath  with  small  bristles  or  tenters,  like  the 
wire  teeth  of  a  card  for  working  wool,  which,  having  a 
contrary  direction  to  the  claws,  and  both  pulling  different 
ways,  if  there  be  any  irregularity  or  yielding  in  the  surface 
of  a  body,  enable  the  fly  to  suspend  itself  very  firmly." 
He  supposed  that  the  most  perfectly  polished  glass  pre- 
sented such  irregularities,  and  that  it  was  moreover  always 
covered  with  a  "  smoky  tarnish,"  into  which  the  hairs  of 
the  foot  penetrated. 

The  "  smoky  tarnish "  is  altogether  gratuitous ;  and 
Mr.  Blackwall  has  exploded  the  idea  of  atmospheric  pres- 
sure, for  he  found  that  flies  could  walk  up  the  interior  of 
the  exhausted  receiver  of  an  air-pump.  He  had  explained 
their  ability  to  climb  up  vertical  polished  bodies  by  the 
mechanical  action  of  the  minute  hairs  of  the  inferior  sur- 
face of  the  palms  ;  but  further  experiments  having  shown 
him  that  flies  cannot  walk  up  glass  which  is  made  moist 
by  breathing  on  it,  or  which  is  thinly  coated  with  oil  or 
flour,  he  was  led  to  the  conclusion  that  these  hairs  are  in 
fact  tubular,  and  excrete  a  viscid  fluid,  by  means  of  which 
they  adhere  to  dry  polished  surfaces ;  and  on  close  inspec- 
tion with  an  adequate  magnifying  power,  he  was  always 
able  to  discover  traces  of  this  adhesive  material  on  the 
track  on  glass  both  of  flies  and  various  other  insects 
furnished  with  pulvilli,  and  of  those  spiders  which  possess 
a  similar  faculty.! 

In  the  earlier  editions  of  Kirby  and  Spence's  "  Intro- 
duction to  Entomology,"  Mr.  Kirby  had  adopted  the  suc- 

*  «  Anim.  Biogr."  f  "  ^inn.  Trans.,"  xvi.  490,  768. 


INSECTS :    THEIR    FEET.  Ill 

torial  hypothesis.  But  in  a  late  one  he  made  an  allusion 
to  Mr.  Blackwall's  opinion,  and  added  the  following  inte- 
resting note : — 

"  On  repeating  Mr.  Blackwall's  experiments,  I  found, 
just  as  he  states,  that  when  a  pane  of  glass  of  a  window 
was  slightly  moistened  by  breathing  on  it,  or  dusted  with 
flour,   bluebottle-flies,   the  common  house-flies,  and  the 
common  bee-fly  (Eristalis  tenax),  all  slipped  down  again 
the  instant  they  attempted  to  walk  up  these  portions  of  the 
glass  ;   and  I  moreover  remarked   that   each  time,  after 
thus  slipping  down,  they  immediately  began  to  rub  first 
the  two  fore  tarsi  and  then  the  two  hind  tarsi  together,  as 
flies  are  so  often  seen  to  do,  and  continued  this  operation 
for  some  moments  before  they  attempted  again  to  walk. 
This  last   fact  struck  me  very  forcibly,  as  appearing  to 
give  an  importance  to  these  habitual  procedures  of  flies 
that  has  not  hitherto,  as  far  as  I  am  aware,  been  attached 
to  them.     These  movements  I  had    always  regarded  as 
meant  to  remove  any  particle  of  dust  from  the  legs,  but 
simply  as  an  affair  of  instinctive  cleanliness,  like  that  of 
the  cat  when  she  licks  herself,  and  not  as   serving  any 
more  important  object ;  and  such  entomological  friends  as 
I  have  had  an  opportunity  of  consulting  tell  me  that  their 
view  of  the  matter  was  precisely  the  same ;  nor  does  Mr. 
Blackwall  appear  to  have  seen  it  in  a  different  light,  since, 
though  so  strongly  bearing  on  his  explanation  of  the  way 
in  which  flies  mount  smooth  vertical  surfaces,  he  never  at 
all  refers  to  it.    Yet,  from  the  absolute  necessity  which  the 
flies  on  which  I  experimented  appeared  to  feel  of  cleaning 
their  pulvilli  immediately  after  being  wetted  or  clogged 
with  flour,  however  frequently  this  occurred,  there  cer- 
tainly seems  ground  for  supposing  that  their  usual  and 
frequent  operation  for  effecting  this  by  rubbing  their  tarsi 
together  is  by  no  means  one  of  mere  cleanliness  or  amuse- 
ment, but  a  very  important  part  of  their  economy,  essen- 
tially necessary  for  keeping  their  pulvilli  in  a  fit  state  for 


112  EVENINGS    AT    THE    MICROSCOPE. 

climbing  up  smooth  vertical  substances  by  constantly  re- 
moving from  them  all  moisture,  and  still  more  all  dust, 
which  they  are  perpetually  liable  to  collect.  In  this 
operation  the  two  fore  and  two  hind  tarsi  are  respectively 
rubbed  together  for  their  whole  length,  whence  it  might 
be  inferred  that  the  intention  is  to  remove  impurities  from 
the  entire  tarsi;  but  this  I  am  persuaded  is  not  usually 
the  object,  which  is  simply  that  of  cleaning  the  under 
side  of  the  pulvilli,  by  rubbing  them  backward  and  for- 
ward along  the  whole  surface  of  the  hairs  with  which  the 
tarsi  are  clothed,  and  which  seem  intended  to  serve  as  a 
brush  for  this  particular  purpose.  Sometimes,  indeed, 
when  the  hairs  of  the  tarsi  are  filled  with  dust  throughout, 
the  operation  of  rubbing  them  together  is  intended  to 
cleanse  these  hairs ;  because,  without  these  brushes  were 
themselves  clean,  they  could  not  act  upon  the  hairs  of  the 
under  side  of  the  pulvilli.  Of  this  I  witnessed  an  inte- 
resting instance  in  an  Eristalis  tenax,  which,  by  walking 
on  a  surface  dusted  with  flour,  had  the  hairs  of  the  whole 
length  of  the  tarsi,  as  well  as  the  pulvilli,  thus  clogged 
with  it.  After  slipping  down  from  the  painted  surface  of 
the  window-frame  which  she  in  vain  attempted  to  climb, 
she  seemed  sensible  that  before  the  pulvilli  could  be 
brushed,  it  was  requisite  that  the  brushes  themselves 
should  be  clean,  and  full  two  minutes  were  employed  to 
make  them  so  by  stretching  out  her  trunk,  and  passing 
them  repeatedly  along  its  sides,  apparently  for  the  sake  of 
moistening  the  flour  and  causing  its  grains  to  adhere  ;  for 
after  this  operation,  on  rubbing  her  tarsi  together,  which 
she  next  proceeded  to  do,  I  saw  distinct  little  pellets  of 
flour  fall  down.  A  process  almost  exactly  similar  I  have 
always  seen  used  by  bluebottle-flies  and  common  house- 
flies  which  had  their  tarsi  clogged  with  flour  by  walking 
over  it,  or  by  having  it  dusted  over  them  ;  but  these 
manoeuvres  are  required  for  an  especial  purpose,  and  on 
ordinary  occasions,  as  before  observed,  the  object  in 


INSECTS  :    THEIR    FEET.  113 

rubbing  the  tarsi  together  is  not  to  clean  them,  but  the 
pulvilli,  for  which  they  serve  as  brushes.  Besides  rubbing 
the  tarsi  together,  flies  are  often  seen,  while  thus  em- 
ployed, to  pass  the  two  fore  tarsi  and  the  tibiae,  with 
sudden  jerks,  over  the  back  of  the  head  and  eyes,  and  the 
two  hind  tarsi  and  tibiae  over  and  under  the  wings,  and 
especially  over  their  outer  margins,  and  occasionally  also 
over  the  back  of  the  abdomen.  That  one  object  of  these 
operations  is  to  clean  these  parts  from  dust,  I  have  no 
doubt,  as  on  powdering  the  flies  with  flour  they  thus 
employ  themselves,  sometimes  for  ten  minutes,  in  detach- 
ing every  part  of  it  from  their  eyes,  wings,  and  abdomen ; 
but  I  am  also  inclined  to  believe  that,  in  general,  when 
this  passing  of  the  legs  over  the  back  of  the  head  and 
outer  margin  of  the  wings  takes  place  in  connexion  with 
the  ordinary  rubbing  of  the  tarsi  together,  as  it  usually 
does,  that  the  object  is  rather  for  the  purpose  of  complet- 
ing the  entire  cleansing  of  the  tarsal  brushes  (for  which 
the  row  of  strong  hairs  visible  under  a  lens  on  the  exterior 
margin  of  the  wings  seems  well  adapted),  so  that  they 
may  act  more  perfectly  on  the  pulvilli.  Here,  too,  it 
should  be  noticed,  in  proof  of  the  importance  of  all  the 
puhilli  being  kept  clean,  that  as  the  tarsi  of  the  two 
middle  legs  cannot  be  applied  to  each  other,  flies  are  con- 
stantly in  the  habit  of  rubbing  one  of  these  tarsi  and  its 
piilriRus,  sometimes  between  the  two  fore  tarsi,  and  at 

other  times  between  the  two  hind  ones 

"  Though  the  above  observations,  hastily  made  on  the 
spur  of  the  occasion  since  beginning  this  note,  seem  to 
prove  that  it  is  necessary  the  pulvilli  of  flies  and  of  some 
other  insects  should  be  kept  free  from  moisture  and  dust 
to  enable  them  to  ascend  vertical  polished  surfaces,  they 
cannot  be  considered  as  wholly  settling  the  question  as  to 
the  precise  way  in  which  these  pulvilli,  and  those  of  in- 
sects generally,  act  in  effecting  a  similar  mode  of  progres- 
sion ;  and  my  main  reason  for  here  giving  these  slight 

i 


H4  EVENINGS    AT    THE    MICROSCOPE. 

hints  is  the  hope  of  directing  the  attention  of  entomologi- 
cal and  microscopical  observers  to  a  field  evidently,  as  yet, 
so  imperfectly  explored. 

''After  writing  the  above,  intended  as  a  conclusion  of 
this  note,  I  witnessed  to-day  (July  11,  1842)  a  fact  which 
I  cannot  forbear  adding  to  it.  Observing  a  house-fly  on 
the  window,  whose  motions  seemed  very  strange,  I  ap- 
proached it,  and  found  that  it  was  making  violent  contor- 
tions, as  though  every  leg  were  affected  with  St.  Vitus's 
dance,  in  order  to  pull  its  pulvilli  from  the  surface  of  the 
glass,  to  which  they  adhered  so  strongly  that  though  it 
could  drag  them  a  little  way,  or  sometimes  by  a  violent 
effort  get  first  one  and  then  another  detached,  yet  the 
moment  they  were  placed  on  the  glass  again  they  adhered 
as  if  their  under  side  were  smeared  with  bird-lime.  Once 
it  succeeded  in  dragging  off  its  two  fore-legs,  when  it 
immediately  began  to  rub  the  pulvilli  against  the  tarsal 
brushes  ;  but  on  replacing  them  on  the  glass  they  adhered 
as  closely  as  before,  and  it  was  only  by  efforts  almost  con- 
vulsive, and  which  seemed  to  threaten  to  pull  off  its  limbs 
from  its  body,  that  it  could  succeed  in  moving  a  quarter 
of  an  inch  at  a  time.  After  watching  it  with  much  interest 
for  five  minutes,  it  at  last  by  its  continued  exertions  got  its 
feet  released  and  flew  away,  and  alighted  on  a  curtain,  on 
which  it  walked  quite  briskly,  but  soon  again  flew  back  to 
the  window,  where  it  had  precisely  the  same  difficulty  in 
pulling  its  pulvilli  from  the  glass  as  before ;  but  after 
observing  it  some  time,  and  at  last  trying  to  catch  it,  that 
I  might  examine  its  feet  with  a  lens,  it  seemed  by  a  vigor- 
ous effort  to  regain  its  powers,  and  ran  quite  actively  on 
the  glass,  and  then  flying  away  I  lost  sight  of  it.  I  am 
unable  to  give  any  satisfactory  solution  of  this  singular 
fact.  The  season,  and  the  fly's  final  activity,  preclude 
the  idea  of  its  arising  from  cold  or  debility,  to  which 
Mr.  White  attributes  the  dragging  of  flies'  legs  at  the  close 
of  autumn.  The  pulvilli  certainly  had  much  more  the 


INSECTS  :    THEIR    FEET.  115 

appearance  of  adhering  to  the  glass  by  a  viscid  material 
than  by  any  pressure  of  the  atmosphere,  and  it  is  so  far  in 
favour  of  Mr.  BlackwalTs  hypothesis,  on  which  one  might 
conjecture  that  from  some  cause  (perhaps  of  disease)  the 
hairs  of  the  pulvitti  had  poured  out  a  greater  quantity  of 
this  viscid  material  than  usual,  and  more  than  the  muscu- 
lar strength  of  the  fly  was  able  to  cope  with."  * 

In  the  foot  of  the  fly  tinder  our  own  observation,  you 
may  see  how  well  the  joints  of  the  tarsus  are  covered  with 
hairs,  or  rather  stiff  pointed  spines,  of  various  dimensions 
and  distances  apart,  and  hence  how  suitable  these  are  for 
acting  the  part  of  combs  to  cleanse  the  palms.  But  these 
last  are  the  organs  that  most  claim  and  deserve  our 
examination.  In  the  specimen  of  the  little  Musca  that  I 
have  imprisoned,  the  last  tarsal  joint  is  terminated  by  two 
strong  divergent  hooks  which  are  themselves  well  clothed 
with  spines,  and  by  two  membranous  flaps  or  palms  be- 
neath them.  These  are  nearly  oval  in  outline,  though  in 
some  species  they  are  nearly  square,  or  triangular,  and  in 
some  of  a  very  irregular  shape.  They  are  thin,  mem- 
branous, and  transparent,  and  when  a  strong  light  is  re- 
flected through  them,  we  see  their  structure  under  this 
power  of  600  diameters  very  distinctly. 

The  inferior  surface  of  the  palm,  on  which  we  are  now 
looking,  is  divided  into  a  vast  number  of  lozenge- shaped 
areas,  which  appear  to  be  scales  overlapping  each  other, 
or  they  may  be  divided  merely  by  depressed  lines.  From 
the  centre  of  each  area  proceeds  a  very  slender,  soft,  and 
flexible  pellucid  filament,  which  reaches  downwards  to  the 
surface  on  which  the  fly  is  walking,  and  is  there  slightly 
hooked  and  enlarged  into  a  minute  fleshy  bulb.  Those 
from  the  areas  near  and  at  the  margins  of  the  palms  more 
and  more  arch  outwards,  so  that  the  space  covered  by  the 
bulbs  of  the  filaments  is  considerably  greater  than  that  of 
the  palm  itself. 

*  "  Introd.  to  Entom.,"  7th  Ed.,  458. 

i2 


116  EVENINGS   AT    THE    MICROSCOPE. 

Now  it  is  evident  that  the  bulbous  extremities  of  these 
soft  filaments  are  the  organs  of  adhesion.  We  notice  how 
they  drag  and  hold,  as  the  fly  draws  its  foot  from  its 
place ;  and  it  seems  almost  certain  that  the  adhesion  is 
effected  by  means  of  a  glutinous  secretion  poured  out  in 
minute  quantities  from  these  fleshy  tips.  When  the  foot 
is  suddenly  removed,  we  may  often  see  a  number  of  tiny 
particles  of  fluid  left  on  the  glass  where  the  filaments  had 
been  in  contact  with  it :  but  I  do  not  build  conclusively 
on  this  appearance,  because  the  fly,  having  been  confined 
for  some  quarter  of  an  hour  in  this  nearly  tight  glass  cell, 
has  doubtless  inhaled  some  moisture,  which  has  condensed 
on  the  glass ;  and  the  specks  we  see  may  possibly  be  due 
to  the  filaments  of  the  palms  having  become  wet  by  re- 
peatedly brushing  the  moist 
surface.  Mr.  Hep  worth,  how- 
ever, asserts  that  a  fluid  is 
poured  out  from  these  fila- 
ments, and  is  deposited  on 
the  glass,  when  the  fly  is  vi- 
gorous, with  great  regularity. 
He  says  that  "  when  in  a 
partially  dormant  state,  the 
insect  does  not  appear  to  be 
able  to  give  out  this  secretion, 
though  it  can  still  attach  it- 
self :  indeed,  this  fluid  is  not 
essential  for  that  purpose."  * 
It  is  asserted  that  the  speckled 
pattern  of  fluid  left  on  the 
glass  by  the  fly's  footsteps  re- 
mains (if  breathed  on)  when 
the  moisture  is  evaporated; 
and  hence  it  is  presumed  to  be  of  an  oily  nature. 

In  some  Beetles  the  joints  of  the  foot  are  furnished  with 
*  "  Micros.  Journal "  for  April,  1854. 


INSECTS:  THEEB  FEET.  117 

similar  appendages.  I  shall  now  show  you  the  fore-foot 
of  a  well-known  insect,  called  by  children  the  Bloody-nose 
Beetle  (Timarcha  tenebricosa),  a  heavy-bodied  fellow,  of  a 
blue-black  colour,  abundant  in  spring  and  summer  on 
hedge-banks.  You  have  doubtless  often  observed  it,  and 
have  been  amused,  perhaps,  at  seeing  the  drop  of  clear 
scarlet  fluid  which  exudes  from  its  mouth  when  touched. 

The  feet  in  this  species  are  broad  and  well-developed. 
You  may  see  with  the  naked  eye,  on  turning  it  up,  that 
its  dilated  joints  are  covered  on  the  under  surface  with  a 
velvety  cushion  of  a  rusty-brown  colour  ;  and  here,  under 
a  low  power  of  the  microscope  with  the  Lieberkiihn,  you 
can  determine  the  nature  of  the  velvet. 

The  foot,  or  tarsus,  as  it  is  technically  called,  is  com- 
posed of  four  very  distinct  pieces ;  of  which  the  first  is 
semicircular,  the  second  crescent-shaped,  the  third  heart- 
shaped,  and  the  fourth  nearly  oval.  The  last  is  rounded 
on  all  sides,  has  no  cushioned  sole,  and  carries  two  stout 
hooks.  The  first  three  are  flat  or  even,  hollowed  beneath 
into  soles,  something  like  the  hoof  of  a  horse,  and  the 
whole  interior  bristles  with  close- set  minute  points,  the 
tips  of  which  terminate  at  the  same  level,  and  form  a 
velvety  surface.  Now,  these  points  are  the  whitish  bulbous 
extremities  exactly  answerable  to  those  on  the  palms  of 
the  fly,  and  doubtless  they  answer  the  very  same  purpose. 
Only  here  they  are  set  in  far  closer  array,  and  are  a  hun- 
dred times  more  numerous;  whence  we  may  reasonably 
presume  a  higher  power  of  adhesion  to  be  possessed  by 
the  beetle.  The  structure  is  best  seen  in  the  male,  which 
may  be  distinguished  by  its  smaller  dimensions,  and  by  its 
broader  feet. 

A  still  better  example  of  a  sucking  foot  is  this  of  the 
Dyticus  marginalia.  It  is  the  great  flat  oval  beetle,  which 
is  fond  of  coming  up  to  the  surface  of  ponds,  and  hanging 
there  by  the  tail  with  its  pair  of  hind  legs  stuck  out  on 
each  side  at  right  angles  ;  the  redoubtable  monster  which 


118 


EVENINGS   AT    THE    MICROSCOPE. 


little  boys  who  bathe  hold  in  such  salutary  awe  under  the 
name  of  Toe -biter.  We  have  turned  the  tables  upon  the 
warrior,  and  have  bitten  his  toe — off,  and  here  it  is.  This 
is  the  tarsus  of  one  of  the  fore  limbs. 

The  peculiarity  that  first  strikes  us  is  that  the  first 
three  joints  are  as  it  were  fused  into  one,  and  spread  out 
so  as  to  make  a  large  roundish  plate.  The  under  surface 
of  this  broad  plate  is  covered  with  a  remarkable  array  of 


FOOT   OF   WATER-BEETLE. 

Large  Sucker,    bb.  Two  smaller  suckers. 
c.  Small  crowded  suckers. 


2.  One  of  the  last  more 
enlarged. 


sucking-disks,  of  which  one  is  very  large,  occupying  about 
a  fourth  part  of  the  whole  area.  It  is  circular,  and  its 
face  is  strongly  marked  with  numerous  fibres  radiating 
from  the  centre.  Near  this  you  perceive  two  others  of 
similar  form  of  structure,  but  not  more  than  one -tenth 


INSECTS  I    THEIB    FEET.  119 

part  of  its  size ;  one  of  these,  moreover,  is  smaller  than 
the  other.  Indeed,  the  size  and  number  of  these  organs 
differ  in  different  individuals  of  the  same  species. 

The  greater  number  of  the  suckers  are  comparatively 
minute ;  but  they  are  proportionally  multitudinous  and 
crowded.  Each  consists  of  a  club-shaped  shaft,  with  a 
circular  disk  of  radiating  fibres  attached  to  its  end.  The 
whole  apparatus  constitutes  a  very  effective  instrument  of 
adhesion. 

There  is  a  somewhat  similar  dilation  of  the  first  joints 
of  the  tarsus,  but  for  a  very  different  object,  in  the  Honey- 
bee ;  and  it  is  particularly  worthy  to  be  observed,  not  only 
for  the  interesting  part  which  it  plays  in  the  economy 
of  the  insect,  but  for  the  example  it  affords  us  of  the 
adaptation  of  one  and  the  same  organ  to  widely  different 
uses,  by  a  slight  modification  of  its  structure. 

It  is  the  hind  foot  of  the  Bee  that  we  are  now  to  ex- 
amine. The  first  joint  is,  as  you  see,  enlarged  into  a 
wide,  long,  and  somewhat  ovate  form,  constituting  a  flattish 
plate,  slightly  convex  on  both  surfaces.  The  upper  face 
presents  nothing  remarkable,  but  the  under  side  is  set 
with  about  nine  stiff  combs,  the  teeth  of  which  are  horny 
straight  spines,  set  in  close  array,  and  arranged  in  trans- 
verse rows  across  the  joint,  nearly  on  a  level  with  its 
plane,  but  a  little  projecting,  and  so  ordered  that  the  tips 
of  one  comb  slightly  overlap  the  bases  of  the  next.  We 
see  them  hi  this  example  very  distinct,  because  their 
colour,  a  clear  reddish-brown,  contrasts  with  a  multitude 
of  tiny  globules  of  a  pale  yellow  hue,  like  minute  eggs, 
which  are  entangled  in  the  combs. 

Now  these  globules  serve  to  illustrate  the  object  of  this 
apparatus.  They  are  grains  of  pollen ;  the  dust  that  is 
discharged  from  the  anthers  of  flowers,  which  being 
kneaded  up  with  honey,  forms  the  food  of  the  maggot  of 
the  Bee,  and  is,  therefore,  collected  with  great  persever- 
ance by  the  industrious  insect ;  and  the  way  in  which  it 


120  EVENINGS   AT    THE    MICROSCOPE. 

collects  it  is,  by  raking  or  combing  it  from  the  anthers,  by 
means  of  these  effective  instruments  on  its  hind  feet. 

You  see  that  in  this  specimen  the  combs  are  loaded 
with  the  grains,  which  lie  thickly  in  the  furrows  between 
one  comb  and  another.  But  how  do  they  discharge  their 
gatherings  ?  Do  they  return  to  the  hive  as  soon  as  they 
have  accumulated  a  quantity  such  as  this,  which  one 
would  suppose  they  could  gather  in  two  or  three  scrapes 
of  the  foot  ?  No  ;  they  carry  a  pair  of  panniers,  or  col- 
lecting baskets,  which  they  gradually  fill  from  the  combs, 
and  then  return  to  deposit  the  results  of  their  collecting. 

One  of  these  baskets  I  can  show  you ;  and,  indeed,  it 
would  be  unpardonable  to  overlook  it,  for  it  is  the  com- 
panion structure  to  the  former.  I  make  the  stage  forceps 
to  revolve  on  its  axis,  and  thus  bring  into  focus  the  joint 
(tibia)  immediately  above  that  of  the  combs,  and  so  that 
we  shall  look  at  its  opposite  surface ;  that  is,  the  outer. 
We  notice  at  once  two  or  three  peculiarities,  which  dis- 
tinguish the  joint  in  this  instance  from  other  parts  of  the 
same  limb,  and  from  the  corresponding  part  in  the  same 
limb  of  other  insects. 

First,  the  surface  is  decidedly  concave,  whereas  it  is 
ordinarily  convex.  Secondly,  this  concave  surface  is 
smooth  and  polished  (except  that  it  is  covered  with  a 
minute  network  of  crossed  lines),  not  a  single  hair,  even 
the  most  minute,  can  be  discerned  in  any  part ;  whereas 
the  corresponding  surface  of  the  next  joints,  both  above 
and  below,  is  studded  with  fine  hairs,  as  is  the  exterior  of 
insects  generally.  Thirdly,  the  edges  of  this  hollowed 
basin  are  beset  with  long,  slender,  acute  spines,  which 
follow  the  same  curve  as  the  bottom  and  sides,  expanding 
widely,  and  arching  upward. 

Here,  then,  we  have  a  capital  collecting  basket.  Its 
concavity  of  course  fits  it  to  contain  the  pollen.  Then  its 
freedom  from  hairs  is  important :  hairs  would  be  out  of 
place  in  the  concavity.  Thirdly,  the  marginal  spines 


INSECTS  I    THEIB   FEET.  121 

greatly  increase  the  capacity  of  the  vessel  to  receive  the 
load,  on  the  principle  of  the  sloping  stakes  which  the 
farmer  plants  along  the  sides  of  his  waggon  when  he  is 
going  to  carry  a  load  of  hay  or  corn. 

But,  you  ask,  how  can  the  Bee  manage  to  transfer  the 
pollen  from  the  combs  to  the  basket  ?  Can  she  bend  up 
the  tarsus  to  the  tibia  ?  or,  if  she  can,  surely  she  could 
only  reach  the  inner,  not  the  outer  surface  of  the  latter. 
How  is  this  managed  ? 

A  very  shrewd  question.  Truth  to  say,  the  basket 
you  have  been  looking  at  never  received  a  single  grain 
from  the  combs  of  the  joint  below  it.  But  the  Bee  has  a 
pair  of  baskets  and  a  pair  of  comb-joints.  It  is  the  right 
set  of  combs  that  fills  the  left  basket,  and  vice  versa.  She 
can  easily  cross  her  hind-legs,  and  thus  bring  the  tarsus 
of  one  into  contact  with  the  tibia  of  the  other  ;  and  if  you 
will  pay  a  moment's  more  attention  to  the  matter,  you 
will  discover  some  further  points  of  interest  in  this  beau- 
tiful series  of  contrivances  stilL  If  you  look  at  this  living 
Bee,  you  notice  that,  from  the  position  of  the  joints,  when 
the  insect  would  bring  one  hind-foot  across  to  the  other, 
the  under  surface  of  the  tarsus  would  naturally  scrape  the 
edge  of  the  opposite  tibia  in  a  direction  from  the  basis  of 
the  combs  towards  their  tips ;  and,  further,  that  the  edge 
of  the  tibia  so  scraped  would  be  the  hinder  edge,  as  the 
leg  is  ordinarily  carried  in  the  act  of  walking.  * 

Now,  if  you  take  another  glance  at  the  basket-joint  in 
the  forceps  of  the  microscope,  you  will  see — what,  perhaps, 
you  have  already  noticed — that  the  marginal  spines  have 
not  exactly  the  same  curvature  on  the  two  opposite  edges, 
but  that  those  of  the  one  edge  are  nearly  straight,  or  at 
most  but  slightly  bowed,  whereas  those  of  the  opposite 
edge  are  strongly  curved,  the  arc  in  many  of  them  reach- 
ing even  to  a  semicircle,  so  that  their  points,  after  per- 
forming the  outward  arch,  return  to  a  position  perpendi- 
cularly over  the  medial  line  of  the  basket. 


122  EVENINGS   AT    THE    MICROSCOPE. 

It  is  the  outer  or  hinder  edge  of  the  joint  that  carries  the 
comparatively  straight  spines.  These  receive  the  grains 
from  the  combs,  which,  then  falling  into  the  basket,  are 
received  into  the  wide  concavity  formed  partly  by  its 
bottom  and  sides,  but  principally  by  the  arching  spines  of 
the  opposite  edge.  Their  curving  form  would  have  been 
less  suitable  than  the  straighter  one  to  pass  through  the 
interstices  of  the  combs,  because  it  would  be  much  more 
difficult  to  get  at  their  points  ;  while,  on  the  other  hand, 
the  straight  lines  of  these  would  have  been  far  less  effec- 
tive as  a  receiver  of  the  burden.  The  thickness  of  the 
spines  is  just  that  which  enables  them  to  pass  freely 
through  the  interstices  of  the  comb-teeth,  and  no  more. 

On  the  whole,  this  combination  of  contrivances  reads  us 
as  instructive  a  lesson  on  the  wisdom  of  God  displayed 
in  creation  as  any  that  we  have  had  brought  under  our 
observation. 

The  end  to  be  attained  by  all  this  apparatus  is  worthy 
of  the  wondrous  skill  displayed  in  its  contrivance  ;  for  it 
is  connected  with  the  feeding  of  the  stock,  and  whatever 
diminishes  the  labour  of  the  individual  bees,  enables  a 
larger  number  to  be  supported.  But  valuable  as  is  the 
Honey-bee  to  man,  there  are  other  important  purposes  to 
be  accomplished,  which  are  more  or  less  dependent,  colla- 
terally, on  this  series  of  contrivances. 

"  In  many  instances  it  is  only  by  the  bees  travelling 
from  flower  to  flower  that  the  pollen  and  farina  is  carried 
from  the  male  to  the  female  flowers,  without  which  they 
could  not  fructify.  One  species  of  bee  would  not  be  suffi- 
cient to  fructify  all  the  various  sorts  of  flowers,  were  the 
bees  of  that  species  ever  so  numerous ;  for  it  requires 
species  of  different  sizes  and  different  construction.  M. 
Sprengel  found  that  not  only  are  insects  indispensable  in 
fructifying  different  species  of  Iris,  but  some  of  them,  as 
I.  Xiphium,  require  the  agency  of  the  larger  humble-bees, 
which  alone  are  strong  enough  to  force  their  way  beneath 


INSECTS  :    THEIR   FEET.  123 

the  style-flag;  and  hence,  as  these  insects  are  not  so 
commmon  as  many  others,  this  Iris  is  often  barren,  or 
bears  imperfect  seeds."* 

The  legs  and  feet  of  Caterpillars  are  constructed  on 
a  very  different  plan  from  those  of  perfect  insects,  as  you 
may  see  in  this  living  Silkworm.  The  first  three  segments 
of  the  body,  reckoning  from  the  head,  are  furnished  each 
with  a  pair  of  short  curved  limbs  set  close  together  on  the 
under  side.  These  represent  the  true  legs  of  the  future 
moth,  and  show,  notwithstanding  their  shortness,  four 
distinct  joints,  of  which  the  last  is  a  little  pointed  horny 
claw.  The  whole  limb  resembles  a  short  stout  hook. 
Then  two  segments  occur  which  are  quite  smooth  be- 
neath, and  destitute  of  limbs  ;  and  then  on  the  sixth  we 
begin  to  find  another  series,  which  goes  on  regularly,  a 
pair  on  each  segment,  to  the  eleventh  and  final  one,  with 
the  single  exception  of  the  tenth  segment,  which  is  again 
deprived  of  limbs. 

But  these  organs  are  of  a  very  peculiar  character.  They 
have  no  representatives  in  the  mature  insect,  but  dis- 
appear with  the  larva  state ;  and  they  are  not  considered 
limbs-proper  at  all,  but  merely  accessory  developments  of 
the  skin  to  serve  a  special  purpose.  They  are  sometimes 
called  claspers,  sometimes  false-legs,  but  more  commonly 
pro-legs. 

Each  consists  of  a  fleshy  wart,  which  is  capable  to  some 
extent  of  being  turned  inside  out,  like  the  finger  of  a 
glove.  Partly  around  the  blunt  and  truncate  extremity 
are  set  two  rows  of  minute  hooks,  occupying  the  side  next 
the  middle  line  of  the  caterpillar  in  a  semicircle  along  the 
margin.  These  hooks  arch  outward  as  regards  the  axis 
of  the  pro-leg,  though  the  majority  of  them  point  towards 
the  medial  line  of  the  body.  The  double  row  is  somewhat 

*  Penny  Cyclop.,  art.  BEE.  Recent  researches  of  Mr.  Darwin  and 
others  have  shown  that  the  agency  of  insects  in  the  fertilisation  of 
plants  is  very  far  more  important  than  had  been  suspected. 


124  EVENINGS   AT    THE   MICROSCOPE. 

interrupted  at  its  middle  point ;  and  just  there,  in  each 
pro-leg,  a  clear  vesicle  or  fleshy  bladder  protrudes  from 
the  sole,  which  may  perhaps  serve  as  a  very  delicate  organ 
of  touch,  or  may  exude  a  viscid  secretion  helpful  to  pro- 
gress on  smooth  bodies.  The  hooks  seem  adapted  to 
catch  and  hold  the  fine  threads  of  silk,  which  most  cater- 
pillars spin  as  a  carpet  for  their  steps. 

In  some  cases  the  circle  of  hooks  is  complete,  as  in  this 
example,  which  I  find  in  one  of  the  slides  of  my  drawer, 
marked  "  Pro-leg  of  a  Caterpillar."  It  is  some  large 
species,  probably  a  Sphinx,  for  the  hooks  are  very  large, 
of  a  clear  orange-brown  hue,  and  set  in  a  long  oval  ring — 
single  as  to  their  basis,  but  double  as  to  their  points — 
completely  around  the  extremity  of  the  foot.  These  hooks 
belong  only  to  the  skin,  as  may  be  well  seen  in  this  pre- 
pared specimen — doubtless  mounted  in  Canada  balsam  ; — 
for  their  roots  are  mere  blunt  points,  set  but  little  below 
the  surface  of  the  thin  skin  without  any  enlargement  or 
apparent  bulb. 


INSECTS:  STINGS  AND  OVIPOSITORS.  125 


CHAPTER  Yd. 

INSECTS  I    STINGS   AND    OVIPOSITORS. 

PROBABLY  at  some  period  of  your  life  you  have  been  stung 
by  a  bee  or  wasp.  I  shall  take  it  for  granted  that  you 
have,  and  that,  having  tasted  the  potency  of  these  warlike 
insects'  weapons  with  one  sense,  you  have  a  curiosity  to 
examine  them  with  another.  The  microscope  shall  aid 
your  vision  to  investigate  the  morbific  implement. 

This  is  the  sting  of  the  Honey-bee,  which  I  have  but 
this  moment  extracted.  It  consists  of  a  dark  brown 
horny  sheath,  bulbous  at  the  base,  but  suddenly  diminish- 
ing, and  then  tapering  to  a  fine  point.  This  sheath  is 
split  entirely  along  the  inferior  edge,  and  by  pressure  with 
a  needle  I  have  been  enabled  to  project  the  two  lancets, 
which  commonly  lie  within  the  sheath.  These  are  two 
slender  filaments  of  the  like  brown  horny  substance,  of 
which  the  centre  is  tubular,  and  carries  a  fluid,  in  which 
bubbles  are  visible.  The  extremity  of  each  displays  a 
beautiful  mechanism,  for  it  is  thinned  away  into  two  thin 
blade-edges,  of  which  one  remains  keen  and  knife-like, 
while  the  opposite  edge  is  cut  into  several  saw-teeth 
pointing  backwards. 

The  lancets  do  not  appear  to  be  united  with  the  sheath 
in  any  part,  but  simply  to  lie  in  its  groove ;  their  basal 
portions  pass  out  into  the  body  behind  the  sheath,  where 
you  see  a  number  of  muscle-bands  crowded  around  them  : 
these,  acting  in  various  directions,  and  being  inserted  into 
the  lancets  at  various  points,  exercise  a  complete  control 
over  their  movements,  projecting  or  retracting  them  at 


126  EVENINGS    AT    THE    MICROSCOPE. 

their  will.  But  each  lancet  has  a  singular  projection 
from  its  back,  which  appears  to  act  in  some  way  as  a 
guide  to  its  motion,  probably  preventing  it  from  slipping 
aside  when  darted  forth,  for  the  bulbous  part  of  the  sheath, 
in  which  these  projections  work,  seems  formed  expressly 
to  receive  them. 

Thus  we  see  an  apparatus  beautifully  contrived  to  enter 
the  flesh  of  an  enemy :  the  two  lancets  finely  pointed, 
sharp- edged,  and  saw-toothed,  adapted  for  piercing,  cut- 
ting, and  tearing  ;  the  reversed  direction  of  the  teeth  gives 
the  weapon  a  hold  in  the  flesh,  and  prevents  it  from  being 
readily  drawn  out.  Here  is  an  elaborate  store  of  power 
for  darting  them  forth  in  the  numerous  muscle-bands; 
here  is  a  provision  made  for  the  precision  of  the  aim ; 
and,  finally,  here  is  a  polished  sheath  for  the  reception  of 
the  weapons  and  their  preservation  when  not  in  actual 
use.  All  this  is  perfect,  but  something  still  was  wanting 
to  render  the  weapons  effective,  and  that  something  your 
experience  has  proved  to  be  supplied. 

The  mere  insertion  of  these  points,  incomparably  finer 
and  sharper  than  the  finest  needle  that  was  ever  polished 
in  a  Sheffield  workshop,  would  produce  no  sensible  result 
on  our  feelings  ;  and  most  surely  would  not  be  followed 
by  the  distressing  agony  attendant  on  the  sting  of  a 
bee.  We  must  look  for  something  more  than  we  have  seen. 

We  need  not  be  long  in  finding  it.  For  here,  at  the 
base  of  the  sheath,  into  which  it  enters  by  a  narrow  neck, 
lies  a  transparent  pear-shaped  bag,  its  surface  covered  all 
over,  but  especially  towards  the  neck,  with  small  glands 
set  transversely.  It  is  rounded  behind,  where  it  is  en- 
tered by  a  very  long  and  slender  membranous  tube,  which, 
after  many  turns  and  windings,  gradually  thickening  and 
becoming  more  evidently  glandular,  terminates  in  a  blind 
end. 

This  is  the  apparatus  for  preparing  and  ejecting  a 
powerful  poison.  The  glandular  end  of  the  slender  tube 


INSECTS  !    STINGS   AND    OVIPOSITORS. 


127 


is  the  secreting  organ  :  here  the  venom  is  prepared ;  the 
remainder  of  the  tube  is 
a  duct  for  conveying  it  to 
the  bag,  a  reservoir  in  which 
it  is  stored  for  the  moment 
of  use.  By  means  of  the 
neck  it  is  thrown  into  the 
groove  at  the  moment  the 
sting  is  projected ;  the  same 
muscles,  probably,  that  dart 
forward  the  weapon  com- 
pressing the  poison-bag,  and 
causing  it  to  pour  forth  its 
contents  into  the  groove, 
whence  it  passes  on  between 
the  two  lancets  into  the 
wound  which  they  have 
made.* 

A  modification  of  this  ap- 
paratus is  found  through- 
out a  very  extensive  order 
of  Insects, — the  Hymeno- 
ptera ;  but  in  the  majority  of 
cases  it  is  not  connected 
with  purposes  of  warfare. 
Wherever  it  occurs  it  is 
always  confined  to  the  female 
sex,  or  (as  in  the  case  of 
some  social  insects)  to  the 
neuters,  which  are  unde- 
veloped females.  When  it 
is  not  accompanied  by  a 

...  PTn«G    OP   BEK. 

pOlSOn  -  reservoir   it   is   USed        <*•  Tip  of  Lancet,  more  enlarged. 

*  Some  further  researches  of  valne  on  the  stings  of  "Wasps  and  Bees, 
with  copious  illustrations,  will  be  found  in  Hardwicke's  Science  Gossip 
for  1868,  p.  148,  by  Dr.  Mills,  p.  205,  by  "S.  8.,"  and  for  1873,  p.  132, 
by  Mr.  Nisbett  Browne. 


128  EVENINGS   AT    THE    MICROSCOPE. 

for  the  deposition  of  the  eggs,  and  is  hence  called  an 
ovipositor,  though  in  many  cases  it  performs  a  part  much 
more  extensive  than  the  mere  placing  of  the  ova. 

In  the  large  tribe  of  Cuckoo-flies  (Ichneumonidce)  which 
spend  their  egg  and  larva  states  in  the  living  bodies  of 
other  insects,  this  ovipositor  is  often  of  great  length  ;  even 
many  times  longer  than  the  rest  of  their  bodies  ;  for  the 
larvae  which  have  to  be  pierced  by  it  require  to  be  reached 
at  the  bottom  of  deep  holes  and  other  recesses  in  which 
the  providence  of  the  parent  had  placed  them  for  security. 
The  structure  of  the  organ  may  be  seen  in  this  little 
species,  not  more  than  one-sixth  of  an  inch  in  entire 
length,  of  which  the  ovipositor  projects  about  a  line. 
Under  the  microscope  you  see  that  this  projection  consists 
of  two  black  fleshy  filaments,  rounded  without  and  flattened 
on  their  inner  faces,  which  are  placed  together,  and  of  the 
true  implement  for  boring,  in  the  form  of  a  perfectly 
straight  awl,  of  a  clear  amber  hue,  very  slender,  and 
brought  to  an  abrupt  oblique  point,  where  there  are  a  few 
exceedingly  fine  reverted  teeth.  It  is  probably  double, 
though  it  refuses  to  open  under  the  pressure  which  I 
bring  to  bear  upon  it.  At  the  base  are  seen  within  the 
semi-pellucid  abdomen  the  slender  horns,  on  which  the 
muscles  act  in  projecting  the  borer. 

You  are  doubtless  aware  that  the  little  berries  which 


GALL-FLY,  AND  MECHANISM  OF  OVIPOSITOR. 

look  like  bunches  of  green  currants,  often  seen  growing  on 


INSECTS  .*    STINGS    AND   OVIPOSITORS.  129 

the  oak,  are  not  the  proper  fruit  of  the  tree,  but  diseased 
developments  produced  by  a  tiny  insect,  for  the  protection 
and  support  of  her  young.  Kirby  and  Spence  tell  us  that 
the  parent  fly  introduces  her  egg  into  a  puncture  made  by 
her  curious  spiral  sting,  and  in  a  few  hours  it  becomes 
surrounded  with  a  fleshy  chamber.  Mr.  Virey  says  the 
gall-tubercle  is  produced  by  irritation,  in  the  same  way  as 
an  inflamed  tumour  in  an  animal  body,  by  the  swelling  of 
the  cellular  tissue,  and  the  flow  of  liquid  matter,  which 
changes  the  organisation,  and  alters  the  natural  external 
form. 

Perhaps  a  still  more  charming  example  of  animal 
mechanics  is  that  furnished  to  us  by  the  Saw-flies  (Ten- 
thredinida).  These  are  very  common  four- winged  insects 
of  rather  small  size,  many  species  of  which  are  found  in 
gardens  and  along  hedges  in  summer,  produced  from 
grubs  which  are  often  mistaken  for  true  caterpillars,  as 
they  strip  our  gooseberry  and  rose  bushes  of  their  leaves  ; 
but  which  may  be  distinguished  from  them  by  the  number 
of  their  pro-legs,  and  by  their  singular  postures  ;  for  they 
possess  from  eight  to  fourteen  pairs  of  the  former  organs, 
and  have  the  habit  of  coiling  up  the  hinder  part  of  their 
body  in  a  spiral  ring,  while  they  hang  on  to  the  leaf  by 
their  six  true  feet. 

These  saw-fly  caterpillars  are  produced  from  eggs  which 
are  deposited  in  grooves  made  by  the  parent  fly  in  the 
bark  of  the  tree  or  shrub  whose  future  leaves  are  destined 
to  constitute  their  food  ;  and  it  is  for  the  construction  of 
these  grooves,  and  the  deposition  of  the  eggs  in  them, 
that  the  curious  mechanism  is  contrived  which  I  am  now 
bringing  under  your  notice. 

Almost  all  our  acquaintance  with  this  instrument  and 
the  manner  of  its  employment,  we  owe  to  the  eminent 
French  naturalist,  Reaumur,  and  to  his  Italian  con- 
temporary, Valisnieri.  Their  details  I  shall  first  cite,  as 
they  have  been  put  into  an  English  dress  by  Rennie,  and 

I 


130  EVENINGS    AT    THE    MICROSCOPE. 

then  show  you  a  specimen  dissected  out  by  myself,  and 
point  out  some  agreements  and  some  discrepancies  between 
it  and  them. 

"  In  order  to  see  the  ovipositor,  a  female  saw-fly  must 
be  taken,  and  her  belly  gently  pressed,  when  a  narrow 
slit  will  be  observed  to  open  at  some  distance  from  the 
anus,  and  a  short,  pointed,  and  somewhat  curved  body, 
of  a  brown  colour  and  horny  substance,  will  be  protruded. 
The  curved  plates  which  form  the  sides  of  the  slit  are 
the  termination  of  the  sheath,  in  which  the  instrument 
lies  concealed  till  it  is  wanted  by  the  insect. 

11  The  instrument  thus  brought  into  view  is  a  very 
finely- contrived  saw,  made  of  horn,  and  adapted  for 
penetrating  branches  and  other  parts  of  plants  where  the 
eggs  are  to  be  deposited.  The  ovipositor- saw  of  the 
insect  is  much  more  complicated  than  any  of  those 
employed  by  our  carpenters.  The  teeth  of  our  saws  are 
formed  in  a  line,  but  in  such  a  manner  as  to  cut  in  two 
lines  parallel  to  and  at  a  small  distance  from  each  other. 
This  is  effected  by  slightly  bending  the  points  of  the 
alternate  teeth  right  and  left,  so  that  one  half  of  the 
whole  teeth  stand  a  little  to  the  right,  and  the  other  half 
a  little  to  the  left.  The  distance  of  the  two  parallel  lines 
thus  formed  is  called  the  course  of  the  saw,  and  it  is  only 
the  portion  of  wood  which  lies  in  the  course  that  is  cut 
into  sawdust  by  the  action  of  the  instrument.  It  will 
follow,  that  in  proportion  to  the  thinness  of  a  saw  there 
will  be  the  less  destruction  of  wood  which  may  be  sawed. 
When  cabinet-makers  have  to  divide  valuable  wood  into 
very  thin  leaves,  they  accordingly  employ  saws  with  a 
narrow  course  ;  while  sawyers  who  cut  planks  use  one 
with  a  broad  course.  The  ovipositor-saw,  being  extremely 
fine,  does  not  require  the  teeth  to  diverge  much,  but 
from  the  manner  in  which  they  operate,  it  is  requisite 
that  they  should  not  stand  like  those  of  our  saws  in  a 
straight  line.  The  greater  portion  of  the  edge  of  the 


INSECTS  :     STINGS    AND    OVIPOSITORS.  131 

instrument,  on  the  contrary,  is  towards  the  point  some- 
what concave,  similar  to  a  scythe,  while  towards  the  base 
it  becomes  a  little  convex,  the  whole  edge  being  nearly 
the  shape  of  an  italic  /. 

"  The  ovipositor-saw  of  the  fly  is  put  in  motion  in  the 
same  way  as  a  carpenter's  hand-saw,  supposing  the 
tendons  attached  to  its  base  to  form  the  handle,  and  the 
muscles  which  put  it  in  motion  to  be  the  hand  of  the 
carpenter.  But  the  carpenter  can  only  work  one  saw  at  a 
time,  whereas  each  of  these  flies  is  furnished  with  two, 
equal  and  similar,  which  it  works  at  the  same  time — one 
being  advanced  and  the  other  retracted  alternately.  The 
secret,  indeed,  of  working  more  saws  than  one  at  once  is 
not  unknown  to  our  mechanics;  for  two  or  three  are 
sometimes  fixed  in  the  same  frame.  These,  however,  not 
only  all  move  upwards  and  downwards  simultaneously, 
but  cut  the  wood  in  different  places :  while  the  two  saws 
of  the  ovipositor  work  in  the  same  cut,  and,  consequently, 
though  the  teeth  are  extremely  fine,  the  effect  is  similar 
to  [that  of]  a  saw  with  a  wide  set  [or  course]. 

"  It  is  important,  seeing  that  the  ovipositor-saws  are  so 
fine,  that  they  be  not  bent  or  separated  while  in  operation  ; 
and  this  also  nature  has  provided  for  by  lodging  the  backs 
of  the  saws  in  a  groove,  formed  by  two  membranous 
plates,  similar  to  the  structure  of  a  clasp-knife.  These 
plates  are  thickest  at  the  base,  becoming  gradually  thinner 
as  they  approach  the  point  which  the  form  of  the  saw 
requires.  According  to  Yalisnieri,  it  is  not  the  only  use 
of  this  apparatus  to  form  a  back  for  the  saws,  he  having 
discovered  between  the  component  membranes  two  canals, 
which  he  supposes  are  employed  to  conduct  the  eggs  of 
the  insect  into  the  grooves  which  she  has  hollowed  out  for 
them. 

"  The  teeth  of  a  carpenter's  saw,  it  may  be  remarked, 
are  simple,  whereas  the  teeth  of  the  ovipositor-saw  are 
themselves  denticulated  with  fine  teeth.  The  latter  also 
K  2 


132  EVENINGS    AT    THE    MICROSCOPE. 

combines  at  the  same  time  the  properties  of  a  saw  and 
of  a  rasp  or  file.  So  far  as  we  are  aware,  these  two 
properties  have  never  been  combined  in  any  of  the  tools  of 
our  carpenters.  The  rasping  part  of  the  ovipositor,  how- 
ever, is  not  constructed  like  our  rasps,  with  short  teeth 
thickly  studded  together,  but  has  teeth  almost  as  long  as 
these  of  the  saw,  and  placed  contiguous  to  them  on  the 
back  of  the  instrument,  resembling  in  their  form  and 
setting  the  teeth  of  a  comb."  * 

Now  look  at  this  object  which  I  have  just  extracted 
from  the  abdomen  of  a  rather  large  female  Saw-fly,  of  a 
bright  green  hue  spotted  with  black.  The  first  portion  of 
the  apparatus  that  protruded  on  pressure  was  this  pair  of 
saws  of  an  y^like  figure.  These  agree  in  general  with 
those  described  ;  here  is  in  each  the  doubly-curved  blade, 
the  strengthened  back,  the  rasp-like  jagging  of  the  lateral 
surfaces,  the  teeth  along  the  edge,  and  the  secondary 
toothlets  of  the  latter.  All  these  essential  elements  we 
see,  but  there  is  much  discrepancy  in  the  detail,  and 
many  points  not  noticed  ;— in  part,  doubtless,  owing  to  its 
being  another  species  which  was  under  observation,  and 
partly  to  the  inferiority  of  the  microscopes  employed  a 
hundred  and  fifty  years  ago  to  those  we  are  using. 

In  the  first  place,  the  curve  of  the  /  is  different,  the 
convexity  of  the  edge  being  towards  the  point  and  the 
concavity  nearest  the  base.  Then  the  strengthening  does 
not  appear  to  me  a  groove  in  which  the  saw  plays,  but 
a  thickening  of  the  substance  of  the  back.  Each  main 
tooth  of  the  saw  in  this  case  is  the  central  point  in  the 
edge  of  a  square  plate,  which  appears  to  be  slightly  con- 
cave on  its  two  surfaces,  being  thickened  at  its  two  sides, 
at  each  of  which,  where  it  is  united  to  the  following  plate, 
it  rises  and  forms  with  it  a  prominent  ridge  running  trans- 
versely to  the  course  of  the  saw.  Each  of  these  ridges  then 
forms  a  second  tooth,  as  stout  as  the  main  edge-tooth, 
*  "  Insect  Architecture,"  153. 


INSECTS:  STINGS  AND  OVIPOSITORS.  138 

which,  with  the  rest  of  the  same  series,  forms  a  row  of 
teeth  on  the  oblique  side  of  the  saw,  in  a  very  peculiar 
manner,  difficult  to  express  by  words.  It  is  singular  that 
this  side  of  the  saw  should  be  studded  with  minute  hairs, 
since  these  would  seem  to  interfere  with  the  action  of 
the  saw,  or  at  least  be  liable  to  be  themselves  rubbed 
down  and  destroyed  in  its  action.  But  their  existence 
is  indubitable ;  there  they  are,  pointing  at  a  very  acute 
angle  towards  the  tip  of  the  saw.  The  back  edge  of  the 
implement  bristles  with  many  close-set  hairs  or  spines, 
forming  a  sort  of  brush,  but  pointing  in  an  opposite 
direction. 

Each  main  tooth  of  the  edge- series  is  cut  into  one  or 
two  minute  toothlets  on  its  posterior  side  (next  the  base 


OUTER  SAW  OP  SAW-FLY. 

a.  A  portion  more  enlarged. 

of  the  saw)  and  about  half-a-dozen  on  its  opposite  side 
(next  the  tip).  The  texture  is  clear  and  colourless  where 
thin  ;  but  in  the  thickened  parts,  as  the  main  teeth,  the 
transverse  ridges,  and  the  back,  it  is  a  clear  amber-yellow  ; 
the  strengthening  back-piece  deepening  to  a  rich  trans- 
lucent brown. 

There  is,  however,  in  this  species  of  mine  a  second  set 
of  implements  of  which  the  French  naturalist,  observant 
as  he  was,  takes  not  the  slightest  notice  ;  and  his  English 


184  EVENINGS   AT    THE    MICROSCOPE. 

commentator  appears  to  have  as  little  suspected  its  pre- 
sence. This  pair  of  saws  that  we  have  been  looking  at  is 
but  the  sheath  of  a  still  finer  pair  of  lancets  or  saws, 
which  you  may  see  here.  These  are  much  more  slender 
than  the  former,  and  are  peculiar  in  their  construction. 


INNER  SAW  OF  SAW-FLY. 


Their  extreme  tip  bears  only  saw-teeth,  and  these  are 
directed  backwards;  but  one  side  of  the  entire  length 
presents  a  succession  of  cutting  edges,  as  if  a  number  of 
short  pieces  of  knife-blade  had  been  cemented  on  a  rod, 
in  such  a  manner  as  that  the  cutting  edges  should  be 
directed  backwards,  and  overlap  each  other.  The  other 
lateral  surface  is  plain,  and  both  are  convex  in  their 
general  aspect.  The  appearance  of  these  implements  is 
very  beautiful,  for  the  texture  is  of  a  clear  pale  amber,  but 
the  structure  is  strengthened  by  a  band  which  runs  along 
each  edge,  and  by  transverse  bands  crossing  at  regular 
intervals,  of  a  denser  tissue;  and  these  are  of  a  rich  golden 
translucent  brown. 

From  the  construction  of  this  implement  I  should  infer 
that  its  force  is  exerted  by  pulling  and  not  by  pushing ; 
the  direction  of  the  teeth  and  of  the  cutting  plates  shows 
this.  The  sharp  horny  point  is  probably  thrust  a  little 
way  into  the  solid  wood  or  bark,  and  then  a  backward  pull 
brings  the  teeth  and  cutting  plates  to  act  upon  the 
material,  and  so  successively.  And  probably  these  points 
are  the  first  parts  of  the  whole  apparatus  that  come  into 
operation ;  the  blunter  saws  of  the  sheath  serving  mainly 


INSECTS:  STINGS  AND  OVIPOSITORS.  185 

to  widen  and  deepen  the  course,  after  the  finer  points  have 
pioneered  the  way. 

The  merry  little  jumping  insects  called  Froghoppers 
(Tettigonia),  one  of  which  in  its  larva  state  emits  the  little 
mass  of  froth  so  common  on  shrubs,  and  called  cuckoo- 
spit,  are  furnished  with  a  set  of  tools  for  their  own  private 
carpentry,  which,  though  less  elaborate  than  those  of  the 
saw-flies,  are  worthy  of  a  moment's  glance.  If  we  catch 
one  of  these  vaulters,  and  gently  press  the  abdomen,  we 
shall  see  proceeding  from  its  hinder  and  lower  part  a 
thickish  piece,  large  compared  with  the  size  of  the  insect, 
which  it  is  then  easy  to  extract  with  a  pair  of  fine- pointed 
pliers.  I  have  just  done  this,  and  here  is  the  result  on  a 
slip  of  glass. 

First,  there  is  a  pair  of  brown  protecting  pieces,  oblong 
in  form,  and  studded  with  hairs  like  the  rest  of  the 
exterior  of  the  body.  From  between  them  projects  what 
resembles  a  lancet,  of  the  usual  translucent  amber- coloured 
horn,  appropriated  to  these  instruments  (which  is  to  them 
what  steel  is  to  us) ;  and  this  we  shall  presently  dis- 
cover to  be  composed  of  two  blades  exactly  alike,  convex 
without  and  concave  within,  applied  face  to  face.  One 
edge  of  this  pair  of  implements  is  quite  smooth,  but  the 
other  is  cut  into  the  most  beautifully  regular  and  most 
minute  teeth. 

This,  however,  is  but  the  sheath.  Within  the  two 
spoon-shaped  faces  there  lie  two  other  lancets,  blade  to 
blade,  still  finer  and  more  delicate.  Both  edges  of  these 
blades  are  of  the  most  perfect  keenness,  without  a  flaw ; 
but  their  sides  appear  roughened  with  rows  of  very  minute 
horny  knobs,  like  a  rasp. 

I  shall  illustrate  this  demonstration  by  another  extract 
from  Reaumur,  premising,  however,  that  his  observations 
refer  to  the  large  species  of  true  Cicada  from  warmer 
latitudes,  whose  machinery  seems  to  differ  from  that  of 
our  little  friends  in  some  particulars.  For  example,  the 


136  EVENINGS   AT    THE    MICROSCOPE. 

two  inner  lancets  seem  to  be  united  in  one,  in  Reaumur's 
species,  or  else,  which  I  think  more  probable,  he  did  not 
succeed  in  separating  them. 

He  describes  the  two  curved  spoon-shaped  pieces  as 
finely  indented  on  both  sides  with  teeth,  which  are  strong, 
nine  in  number,  arranged  with  great  symmetry,  increasing 
in  fineness  towards  the  point.  This  instrument  he  de- 
scribes as  composed  of  three  pieces,  the  two  exterior, 
which  he  calls  the  files,  and  another  pointed,  which  he 
compares  to  a  lancet,  which  is  not  toothed.  "The  files 
are  capable  of  being  moved  forward  and  backward,  while 
the  central  one  remains  stationary ;  and  as  this  motion  can 
be  effected  by  pressing  a  pin  or  the  blade  of  a  knife  over 
the  muscles  on  either  side  at  the  origin  of  the  ovipositor,  it 
may  be  presumed  that  those  muscles  are  destined  for 
producing  similar  movements  when  the  insect  requires 
them.  By  means  of  a  finely-pointed  pin  carefully  intro- 
duced between  the  pieces,  and  pushed  very  gently  down- 
wards, they  may  be,  with  no  great  difficulty,  separated  in 
their  whole  extent. 

"  The  contrivances  by  which  those  three  pieces  are  held 
united,  while  at  the  same  time  the  two  files  can  be  easily 
put  in  motion,  are  similar  to  some  of  our  own  mechanical 
inventions,  with  this  difference,  that  no  human  workman 
could  construct  an  instrument  of  this  description  so  small, 
fine,  exquisitely  polished,  and  fitting  so  exactly.  We  should 
have  been  apt  to  form  the  grooves  in  the  central  piece, 
whereas  they  are  scooped  out  in  the  handles  of  the  files, 
and  play  upon  two  projecting  ridges  in  the  central  piece, 
by  which  means  this  is  rendered  stronger.  M.  Reaumur 
discovered  that  the  best  manner  of  showing  the  play  of 
this  extraordinary  instrument  is  to  cut  it  off  with  a  pair  of 
scissors  near  its  origin,  and  then,  taking  it  between  the 
thumb  and  the  finger  at  the  point  of  section,  work  it  gently 
to  put  the  files  in  motion. 

"Beside  the  muscles  necessary  for  the  movement  of 


INSECTS  I    STINGS   AND    OVIPOSITORS.  137 

the  files,  the  handle  of  each  is  terminated  by  a  curve  of 
the  same  hard  horny  substance  as  itself;  which  not  only 
furnishes  the  muscles  with  a  sort  of  lever,  but  serves  to 
press,  as  with  a  spring,  the  two  files  close  to  the  central 
piece."* 

The  use  of  these  instruments  is  the  same  as  I  have 
already  alluded  to  in  the  case  of  the  saw-flies.  The  female 
Tree-hopper  deposits  her  eggs  in  holes  which  she  bores 
in  dead  twigs  by  means  of  these  files  and  lancets.  The 
branches  chosen  are  said  to  be  easily  known  by  being 
studded  with  little  oblong  elevations,  caused  by  the  partial 
raising  of  a  splinter  of  wood  at  the  orifice  of  the  hole,  to 
which  it  serves  as  a  cover.  These  are  arranged  in  a 
single  line  ;  the  holes  which  they  protect  being  only  half- 
an-inch  in  length,  and  reaching  to  the  pith,  whose  course 
they  then  follow.  Not  more  than  six  or  eight  eggs  are 
laid  in  each  hole ;  but  an  idea  of  the  labours  of  the  in- 
dustrious and  provident  mother  will  be  formed  from  the 
fact  that  she  lays  six  or  seven  hundred  eggs  in  the  course 
of  the  summer. 

*  « Insect  Architecture,"  149. 


138  EVENINGS    AT    THE    MICROSCOPE. 


CHAPTER  IX. 

INSECTS:  THEIR  MOUTHS. 

THE  parts  of  the  mouth  in  different  Insects  afford  an. 
almost  endless  store  of  delightful  observations  ;  and  the 
more  as,  with  all  their  variety,  they  are  found  to  be  in 
every  case  composed  of  the  same  essential  elements. 
You  would  not  think  so  indeed ;  you  would  naturally 
suppose — looking  at  the  biting  jaws  of  a  Beetle,  the 
piercing  proboscis  of  a  Bug,  the  long,  elegantly- coiled 
sucker  of  a  Butterfly,  the  licking  tongue  of  a  Bee,  the 
cutting  lancets  of  a  Horse-fly,  and  the  stinging  tube 
of  a  Gnat — that  each  of  these  organs  was  composed  on 
a  plan  of  its  own,  and  that  no  common  structure  could 
exist  in  instruments  so  diverse.  But  it  is  so,  as  we  shall 
see. 

We  may  consider  the  various  organs  of  the  mouth 
as  most  harmoniously  and  perfectly  developed  in  the 
active  carnivorous  Beetles,  the  Carabida,  or  ground- 
beetles,  for  instance.  Let  us  examine  the  head  of 
this  black  Scarites  from  the  garden ;  and  first  from 
above. 

In  front  of  the  polished  head-shield,  and  jointed  to  it 
by  a  broad  transverse  straight  edge,  is  a  four-sided  piece, 
forming  an  oblong  figure,  nearly  twice  as  broad  as  long, 
a  little  convex,  and  marked  with  six  little  pits  or  sinkings 
of  the  surface,  along  its  front  edge.  This  is  the  upper 
lip  ;  but,  instead  of  being  fleshy,  as  ours  is,  it  is  composed 
of  a  hard  polished  black  shelly  substance,  of  a  peculiar 


INSECTS:  THEIR  MOUTHS.  13jj) 

nature,  called  chitine,  the  same  substance  as  the  hard 
parts  of  all  Insects  and  Crustacea  are  made  of. 

From  beneath  the  sides  of  this  there  project  on  each 
side  two  broad  hooked  pieces,  which,  as  you  see,  I  can 
with  a  needle  force  out  laterally,  so  as  to  show  their  form 
better,  for  they  hinge  upon  the  sides  of  the  face,  beneath 
the  head-shield.  Each  forms  the  half  of  a  crescent,  the 
curved  points  of  which  are  turned  towards  each  other,  and 
can  work  upon  each  other,  the  points  crossing  like  shears. 
These  are  the  proper  biting  jaws,  or  mandibles,  and  in 
many  of  the  larger  beetles  they  have  great  power  of  hold- 
ing and  crushing.  Sometimes  their  inner  side  is  cut  into 
strong  teeth,  but  here  this  side  forms  a  blunt  cutting 
edge ;  the  upper  surface,  however,  is  scored  with  ridges 
and  furrows  like  a  file  ;  and  this  structure  is  best  seen  in 
the  left  jaw,  which,  when  the  pair  close,  crosses  over  the 
right.  This  is  an  action  of  the  jaws  the  reverse  of  ours, 
but  it  is  characteristic  of  all  articulate  animals,  in  which 
the  jaws,  whenever  present,  always  work  horizontally, 
from  right  to  left,  and  not  vertically,  up  and  down. 

I  will  now,  by  making  the  forceps  revolve,  bring  the 
under  side  of  the  head  into  view  ;  for,  without  separating 
the  parts  by  dissection  (which,  however,  is  by  no  means 
difficult),  it  is  impossible  to  see  them  all  from  one  point  of 
view.  The  part  nearest  our  eye  now  is  the  chin,  a  wide 
horny  piece,  like  the  upper  lip,  jointed  to  the  head  by  its 
straight  hind  edge,  but,  unlike  it,  having  its  front  edge 
hollowed  out  with  two  deep  notches,  the  central  piece 
between  them  itself  notched  at  its  tip.  Immediately  above 
this  notched  central  tooth  (I  speak  of  the  relative  position 
of  the  parts,  supposing  the  insect  to  be  crawling  on  the 
ground,  without  reference  to  the  way  in  which  we  turn  it 
about  on  the  microscope),  and  united  with  it,  there  is  a 
sort  of  solid  square  pedestal,  on  which  stand  a  pair  of 
jointed  organs,  and  between  them  an  oblong  horny  plate 
rounded  at  the  tip,  where  it  bears  two  bristles.  This 


140  EVENINGS   AT  THE   MICBOSCOPE. 

latter  is  the  tongue,  while  the  jointed  organs  on  each  side 
are  called  feelers, — palpi;  though  this  is  a  begging  of  the 
question,  for  we  do  not  really  know  the  function  of  these 
organs.  The  chin,  the  tongue  (ligula),  and  these  palpi, 
constitute  together  the  under  lip. 

Between  the  tongue  and  the  biting  jaws,  or  mandibles, 
we  see  a  pair  of  organs  similar  to  these  latter,  but  smaller, 
less  solid,  and  more  curved.  These  are  the  under  or 
secondary  jaws,  maxilla,  the  use  of  which  is  to  hold  the 


MOUTH  OF   BEETLE. 

(Seen  from  beneath.) 

a,  upper  lip  ;  6,  mandibles ;  c,  maxillse ;  d,  maxillary  palpi ;  e,  tongue ; 
/,  labial  palpi ;  g,  chin. 


food,  while  the  biting  jaws  work  on  it,  and  to  convey  it 
when  masticated  to  the  back  of  the  mouth.  Their  whole 
inner  edge  is  set  with  short  stiff  bristles,  which  towards 
the  tips  of  the  jaws  become  spines.  Near  the  bases  of 
these  jaws,  on  the  outer  edge,  are  jointed  two  other  pairs 
of  palpi,  one  pair  to  each  jaw ;  of  which  the  exterior  is 
much  stouter  and  longer  than  the  interior.  Thus  this 


INSECTS  I    THEIR   MOUTHS.  141 

beetle  has  three  pairs  of  these  many-jointed  organs,  the 
labial,  and  the  two  pairs  of  maxillary  palpi. 

Now,  in  this  form  of  mouth,  which  has  been  called  a 
perfect  or  complete  mouth,^-that  is,  one  in  which  all  the 
constituent  parts  can  be  well  made  out,  we  find  the  fol- 
lowing organs  : — 1.  the  upper  lip  (labrum) ;  2.  the  man- 
dibles ;  8.  the  maxilla ;  with  a,  the  maxillary  palpi ;  4.  the 
lower  lip  (labium),  comprising  £,  the  tongue,  y,  the  labial 
palpi,  8,  the  chin  (mentum). 

I  now  exhibit  to  you  the  head  of  the  Honey-bee.  The 
front  is  occupied  by  an  upper  lip,  and  a  pair  of  biting 
jaws  (mandibles),  which  do  not  greatly  differ  from  the 
same  parts  in  a  beetle.  The  jaws,  however,  are  more 
hatchet-shaped,  or  rather  like  the  hoof  of  a  horse,  sup- 
posing the  soles  to  be  the  opposing  surfaces.  The  other 
organs  are  greatly  modified,  so  that  you  would  scarcely 
recognise  them.  The  under  jaws  (maxilla)  are  greatly 
lengthened  ;  and  the  two,  when  placed  in  contact,  form  a 
kiid  of  imperfect  tube,  or  sheath.  Within  these  is  the 
lower  lip,  divided  into  its  constituent  parts  :  the  thick 
opaque  chin,  at  its  basal  end ;  then  the  two  labial  palpi, 
each  consisting  of  four  joints,  of  which  the  two  terminal 
ones  are  minute,  while  the  two  basal  are  large  and  greatly 
lengthened,  so  as  to  resemble  in  appearance  the  maxilla, 
whose  function  they  imitate  also ;  for  the  pair  of  palpi 
when  closed  form  an  inner  sheath  for  the  tongue. 
Finally,  you  see  this  organ,  which  is  the  most  curiously 
developed  and  modified  of  all,  for  it  is  drawn  out  to  a 
long  slender  cylindrical  tube,  formed  of  a  multitude  of 
close-set  rings,  and  covered  with  fine  hairs.  Some  deny 
it  to  be  tubular,  and  maintain  that  it  is  solid ;  but  cer- 
tainly it  appears  to  me  to  have  a  distinct  cavity  through- 
out, with  thickish  walls. 

Under  a  high  power  the  structure  of  the  investing  hairs 
is  very  interesting ;  for  they  are  seen  to  be  flat  filaments 
of  the  yellow  chitine,  very  much  dilated  at  their  bases, 


142 


EVENINGS    AT    THE    MICROSCOPE. 


and  set  side  by  side  in  regular  whorls,  the  bottom  edges 
of  which  form  the  rings  of  which  the  tongue  is  composed. 
The  tip  is  probably  a  sensitive  organ  of  taste,  for  it  ter- 
minates in  a  minute  globose  pulpy  body,  whose  surface  is 
beset  with  tiny  curved  points.  Thus  I  have  pointed  out 
to  you  all  the  parts  which  enter  into  the  mouth  of  the 


JAWS   OF   BEE. 


beetle,  except  the  maxillary  palpi ;  and  these,  very  small 
indeed,  but  quite  distinct,  you  may  see  on  the  outer  edge 
of  the  maxilla,  just  below  the  point  where  their  outline 
begins  to  swell  into  its  graceful  curve. 

The  cylindrical  tongue  is  capable  of  considerable  ex- 


INSECTS  :    THEIR    MOUTHS.  148 

% 

tension  and  contraction  at  the  will  of  the  animal,  being 
sometimes  pushed  far  out  of  the  mouth,  and  at  others 
quite  concealed  within  its  sheath.  "  The  manner,"  ob- 
serves Mr.  Newport,  "  in  which  the  honey  is  obtained, 
when  the  organ  is  plunged  into  it  at  the  bottom  of  a 
flower,  is  by  lapping,  or  a  constant  succession  of  short 
and  quick  extensions  and  contractions  of  the  organ,  which 
occasion  the  fluid  to  accumulate  upon  it,  and  to  ascend 
along  its  upper  surface,  until  it  reaches  the  orifice  of  the 
tube  formed  by  the  approximation  of  the  maxilla  above, 
and  of  the  labial  palpi,  and  this  part  of  the  ligula 
below." 

Well  might  Swammerdam,  when  describing  this  ex- 
quisite structure,  humbly  exclaim: — "I  cannot  refrain 
from  confessing,  to  the  glory  of  the  immense  and  incom- 
prehensible Architect,  that  I  have  but  imperfectly  de- 
scribed and  represented  this  small  organ  ;  for  to  represent 
it  to  the  life  in  its  full  perfection,  as  truly  most  perfect 
it  is,  far  exceeds  the  utmost  efforts  of  human  know- 
ledge." 

Here  you  may  see  the  implement  with  which  the  bug 
performs  its  much-dreaded  operation  of  blood-sucking ; 
for  though  this  is  not  the  head  of  the  Bed-bug,  but  of  one 
of  the  winged  species  that  are  found  so  abundantly  on 
plants,  and  which  I  have  just  obtained  by  beating  the 
hedge  at  the  bottom  of  my  garden,  yet  the  structure 
of  the  mouth  is  so  exactly  alike  in  all  the  members  of 
this  immense  family,  that  one  example  will  serve  for  all 
others. 

From  the  front  of  the  head,  which,  owing  to  the  manner 
in  which  this  part  is  carried,  is  the  lower  part,  proceeds  a 
fine  thread,  about  four  times  as  long  as  the  head  itself, 
and  passing  along  between  the  fore  legs,  close  to  the 
body,  beneath  the  breast.  It  is,  however,  at  the  pleasure 
of  the  animal,  capable  of  being  brought  up  so  as  to  point 
directly  forward,  and  even  projected  in  front  of  the  head, 


144  EVENINGS   AT    THE    MICKOSCOPE. 

and  in  the  same  plane  as  the  body;  a  fact  which  once 
came  under  my  own  observation.  I  found  a  Plant-bug 
(Pentatoma)  which  had  plunged  this  thread-like  sucker  of 
his  into  the  body  of  a  caterpillar,  and  was  walking  about 
with  his  prey,  as  if  it  were  of  no  weight  at  all,  carrying  it 
at  the  end  of  his  sucker,  which  was  held  straight  out  from 
the  head,  and  a  little  elevated.  He  fiercely  refused  to 
allow  the  poor  victim  to  be  taken  away,  being  doubtless 
engaged  in  sucking  its  vital  juices,  just  as  the  bed-abomi- 
nation victimises  the  unfortunates  who  have  to  sleep  at 
some  village  inn. 

Well,  we  put  this  head  with  its  sucker  between  the 
plates  of  the  compressorium,  upon  the  microscope-stage. 
The  thread  is  an  organ  composed  of  four  lengthened 
slender  joints,  beset  with  scattered  bristles,  and  termi- 
nating in  a  point  on  which  are  placed  a  number  of 
exceedingly  minute  radiating  warts,  probably  the  seat  of 
some  sensation;  perhaps  taste.  This  jointed  organ  is  the 
under-lip ;  it  is  slit  all  down  one  surface,  so  that  it  forms 
an  imperfect  tube,  or  furrow,  within  which  lies  the  real 
weapon,  a  wire  of  far  greater  tenuity,  which  by  pressure 
I  can  force  out  of  its  sheath.  It  is  so  slender  that  its 
average  diameter  is  not  more  than  T^Vo-th  of  an  inch,  and 
it  ends  in  the  most  acute  point ;  yet  this  is  not  a  single 
body,  but  consists  of  four  distinct  wires,  lying  within  one 
another,  and  representing  the  maxillae  and  the  mandibles. 
These  can  be  separated  by  the  insect,  and  will  sometimes 
open  when  under  examination ;  but  no  instrument  that  I 
can  apply  to  them  is  sufficiently  delicate  to  effect  their 
separation  at  my  pleasure.  Just  at  the  very  tip,  however, 
under  this  high  power,  we  can  see,  by  the  semi-trans- 
parency of  the  amber-coloured  chitine  of  which  the  organ 
is  composed,  that  there  is  another  tip  a  little  shorter,  and, 
as  it  were,  contained  within  the  other.  This  inner  point 
is  cut  along  its  edges  into  saw-teeth  pointing  backward. 
Such  exquisite  mechanism  is  bestowed  upon  the  structure, 


INSECTS:  THEIR  MOUTHS.  145 

and  such  elaborate  contrivance  is  displayed  for  the  comfort 
of  an  obscure  and  offensive  insect,  by  Him  Who  has  not 
disdained  to  exercise  His  skill  and  wisdom  in  its  creation  ! 

You  know  the  stout  flies  which  are  denominated  Horse- 
flies or  Whame-flies  (Tabanus),  which  are  so  numerous  in 
the  latter  part  of  summer,  flying  around  horses,  and  men 
too,  if  we  intrude  upon  their  domains.  They  are  con- 
tinually alighting  on  the  objects  of  their  attentions,  and 
though  driven  away,  returning  with  annoying  pertinacity 
to  the  attack.  You  may  always  recognise  them  by  the 
brilliant  metallic  hues — reds,  yellows,  and  greens — with 
which  their  large  eyes  are  painted,  often  in  stripes  or 
bands.  These  are  voracious  blood-suckers ;  and,  as  might 
be  supposed  from  their  propensities,  they  are  well  furnished 
with  lancets  for  their  surgery.  Here  you  may  see  their 
case  of  instruments,  which  are  so  effective,  that  Reaumur 
tells  us  that,  having  compelled  one  to  disgorge  the  blood 
it  had  swallowed,  the  quantity  appeared  to  him  greater  than 
the  whole  body  of  the  insect  could  have  been  supposed 
capable  of  containing. 

All  the  parts  here  are  formed  of  the  common  amber- 
coloured  chitine,  brilliantly  clear  and  translucent.  The 
upper  lip  forms  a  sort  of  straight  sheath,  in  which  all  the 
other  parts  are  lodged  when  not  in  use.  The  mandibles 
are  narrow  lancets,  of  which  one  edge  near  the  tip  is  beset 
with  reverted  saw-teeth,  and  the  opposite  edge  with 
exceedingly  sharp  points  standing  out  at  right  angles ; 
while  the  surface  is  roughened  with  lozenge-shaped  knobs 
set  in  regular  rows.  Below  these  are  the  maxilla,  which 
are  the  principal  cutting  instruments ;  these  are  shaped 
like  a  carving-knife  with  a  broad  blade,  strengthened  at 
the  basal  part  of  the  back  by  a  thick  ridge,  but  brought  to 
a  double  edge  near  the  tip.  The  back-edge  is  perfectly 
fine  and  smooth,  so  that  the  highest  powers  of  the  micro- 
scope can  only  just  define  its  outline,  while  the  other  edge 
is  notched  into  teeth  so  delicate  that  twelve  of  them  are 


146  EVENINGS   AT    THE    MICROSCOPE. 

cut  in  the  length  of  a  ten- thousandth  part  of  an  inch ; 
and  yet  they  are  quite  regular  and  symmetrical  in  length, 
height,  and  form  !  I  know  of  no  structure  of  the  kind 
which  equals  this.  These  teeth  are  continued  throughout 
the  inner  edge  of  the  blade  from  the  tip  to  the  base,  and 
are  about  eight  hundred  in  number ;  though  the  length 
of  the  entire  blade  is  only  such  that  upwards  of  a  hundred 
and  fifty  of  them,  if  laid  end  to  end,  would  not  reach  to  the 
extent  of  an  inch  ! 

The  office  of  these  wonderful  instruments  is  doubtless 
to  cut  and  enlarge  the  wound  within,  and  thus  promote 
the  flow  of  blood.  The  whole  apparatus  is  plunged  into 
the  flesh  of  the  victim — horse  or  man  ;  then  the  maxilla 
expand,  cutting  as  they  go,  and  doubtless  working  to  and 
fro  as  well  as  laterally,  so  as  to  saw  the  minuter  blood- 
vessels. At  the  same  time  the  mandibles,  with  their  saw- 
teeth on  one  side,  and  pricking  points  on  the  other,  work 
in  like  manner,  but  seem  to  have  a  wider  range.  Finally, 
there  is  an  exceedingly  delicate  piece  beneath  all,  which 
seems  to  represent  the  labium  or  under  lip. 

In  the  active  and  cunning  little  Flea,  that  makes  his 
attacks  upon  us  beneath  the  shelter  of  the  blankets  and 
under  cover  of  night,  the  piercing  and  cutting  blades  are 
very  minute,  and  have  a  peculiar  armature.  They  remind 
me  (only  in  miniature  of  course)  of  those  formidable  flat 
weapons  which  we  often  see  in  museums — the  rostrums  of 
the  huge  Saw-fishes  (Pristis) ;  a  great  plate  of  bone 
covered  with  grey  skin,  and  set  along  each  side  with  a 
row  of  serried  teeth.  Here  the  blades  are  similar  in  form, 
being  long,  straight,  narrow  plates  of  transparent  chitine, 
set  along  each  edge  with  a  double  row  of  glassy  points, 
which  project  from  the  surface,  and  are  then  hooked  back- 
wards. These  are  the  mandibles,  and  they  closely  fold 
together,  inclosing  another  narrower  blade,  the  upper  lip, 
which  has  its  two  edges  studded  with  similar  points,  but 
in  a  single  row. 


INSECTS  I    THEIR   MOUTHS.  14? 

In  general,  as  we  have  seen,  the  maxilla  are  the  specially 
armed  weapons ;  the  mandibles  acting  a  secondary  part, 
often  serving  as  mere  sheaths  in  those  insects  which 
pierce  other  animals  with  the  mouth.  But  in  this  case 
the  mandibles  are  the  favoured  parts,  the  maxilla  being 
developed  into  broad  leaf- shaped  convex  sheaths,  inclosing 
the  mandibles. 

There  are,  however,  two  cutting  blades  besides ;  the 
labial  palpi,  which  have  their  upper  edge  thick,  divided 
into  four  distinct  joints,  and  set  with  bristles,  thus  re- 
taining the  proper  character  of  palpi ;  while  their  under 
edge  is  thinned  away  to  a  fine  keen  blade,  in  which  there 
is  no  sign  of  jointing.  Then  there  are  the  maxillary 
palpi,  of  which  the  joints  are  furnished  at  their  tips  with 
tiny  projecting  warts,  doubtless  the  seats  of  a  delicate 
sense,  and  hollowed  into  a  double  series  of  chambers, 
which  are  filled  with  a  dark-coloured  fluid. 

All  this  is  very  interesting  to  behold,  and  is  calculated 
to  exalt  our  ideas  of  the  wonderful  and  inexhaustible 
resources  of  Omnipotence,  as  well  as  to  humble  us,  when 
we  reflect  how  little  we  certainly  understand  even  of 
what  we  see.  But,  common  as  the  Flea  is,  it  is  not  a 
matter  of  course  that  you  will  be  able  to  repeat  these 
observations  with  the  first  specimen  you  put  on  the  stage 
of  your  microscope.  Several  favourable  conditions  must 
combine  in  order  to  insure  a  successful  examination. 
You  should  choose  a  female  Flea,  partly  because  of  her 
greater  size,  and  partly  because  the  predatory  weapons, 
in  all  these  piercing  and  sucking  insects,  are  better  de- 
veloped in  the  females, — true  Amazons.  Then  you  will 
find  it  needful  to  amputate  the  head,  in  order  to  get  rid 
of  the  front  legs,  the  thick  thighs  of  which  else  impede 
your  sight  of  the  mouth,  being  projected  on  each  side  of 
it.  And  this  is  a  delicate  operation;  it  must  be  per- 
formed on  a  plate  of  glass,  under  a  lens,  with  one  of 
those  dissecting  needles  whose  points  are  ground  to  a 
L  2 


148  EVENINGS    AT    THE    MICROSCOPE. 

cutting-edge.  Next,  having  severed  the  head,  you  must 
place  it  in  a  drop  of  water,  between  the  plates  of  your 
compressorium,  the  graduated  pressure  of  which,  by 
means  of  the  screw,  will  cause  the  organs  of  the  mouth 
to  open  and  expand  separately.  Finally,  you  must  have 
a  good  instrument,  and  a  high  power :  less  than  600 
diameters  will  not  avail  to  bring  out  distinctly  the  toothing 
of  the  mandibles  and  labrum ;  and  even  then  you  will  need 
delicate  manipulation  and  a  practised  eye.  But  the  object 
is  worthy  of  the  care  bestowed  upon  it. 

Once  more.  Let  us  submit  to  examination  the  complex 
case  of  instruments  wherewith  the  Gnat  performs  her  un- 
welcome yet  skilful  surgery.  I  say  "  her,"  because  among 
the  Gnats  also,  as  I  have  just  intimated,  it  is  the  females 
only  who  possess  skill  in  the  art  of  bleeding ;  the  males 
being  innocent  of  any  share  in  it,  and  being  indeed  unpro- 
vided with  the  needful  implements. 

Here  is  a  large  specimen,  resting  with  raised  hind  legs 
on  the  ceiling,  and  now  in  alarm  off  with  shrill  humming 
flight  to  the  window.  I  decapitate  her  without  com- 
punction, as  it  is  but  a  fair  penalty  for  her  murderous 
deeds ;  and,  as  of  old  the  axeman  held  up  "  the  head  of 
a  traitor"  to  public  gaze,  so  I  lay  this  head  on  the  glass 
of  the  compressorium  for  your  contemplation. 

And  before  I  apply  pressure  to  the  glass-plate,  devote  a 
moment's  attention  to  the  head  as  a  whole.  First,  the 
head  itself  is  a  hemisphere,  almost  wholly  occupied  with 
the  two  compound  eyes,  which  present  the  beautiful  ap- 
pearance of  a  globe  of  black  velvet,  studded  with  gold 
buttons  arranged  in  lines  crossing  each  other  at  right 
angles.  The  summit  of  the  head,  where  the  two  com- 
pound eyes  unite,  bears  a  sort  of  rounded  pedestal,  the 
area  of  which  forms  the  sole  part  of  the  head  not  covered 
by  the  organs  of  vision.  On  this  are  placed,  side  by  side, 
the  two  antennas,  springing  from  rounded  bulbous  bases  ; 
they  consist  of  twelve  (exclusive  of  the  basal  bulb)  cylin- 


INSECTS  I    THEIR    MOUTHS.  149 

drical  joints,  which  are  beset  on  all  sides  with  short  arched 
hairs,  but  have  besides  a  whorl  of  radiating  long  hairs 
surrounding  the  bottom  of  each  joint.  The  effect  of  this 
is  exceedingly  light  and  elegant. 

Between  these  projects  a  long  cylinder,  which  represents 
the  lower  lip  (labium) ;  it  slightly  swells  towards  the  tip, 
where  it  forms  a  round,  nut-like  knob,  covered  with 
exceedingly  minute  papillae,  and  no  doubt  constituting  a 
highly  sensitive  organ  of  touch.  For  the  greatest  part  of 
its  length  it  is  covered  with  lined  scales,  and  with  short 
arched  hairs  like  the  antennae,  while  each  side  of  its  base 
is  guarded  by  a  labial  palp  of  three  joints. 

On  applying  a  graduated  pressure,  slowly  increased  to 
actual  contact  of  the  plates  (or  as  near  an  approximation 
to  it  as  we  can  effect),  we  see  first  that  the  nut-like  tip  of 
the  labium  expands  into  two  concave  leaves,  like  the  bracts 
of  a  bud,  and  displays  two  pairs  of  more  delicate  leaves 
within  them.  Then  from  a  groove  along  the  upper  side 
of  the  labium  spring  out  several  filaments  of  great  elas- 
ticity, and  of  the  most  delicate  tenuity.  One  pair  of  these 
represent  the  mandibles  ;  they  consist  each  of  a  very  nar- 
row blade,  with  a  stronger  back  like  that  of  a  scythe. 
Their  tip  is  brought  to  a  most  acute  point,  and  the  edge 
in  immediate  proximity  to  this  is  cut  into  about  nine  teeth, 
pointing  backward ;  the  rest  of  the  edge  is  smooth,  but 
the  whole  blade  is  crossed  by  a  multitude  of  oblique  lines 
of  great  delicacy,  which  may  be  intended  to  keep  the  edge 
constantly  keen. 

Next  come  the  maxilla,  or  lower  jaws,  horny  filaments 
as  long  as  the  former,  but  still  more  delicate,  constituting 
simple  cutting  lancets,  with  a  back  and  a  keen  blade,  a  little 
widening  at  the  tip. 

Besides  these  there  is  the  tongue,  consisting  of  a 
central  rod  which  is  distinctly  tubular,  and  of  a  thin 
blade  on  each  side,  fine-edged  and  drawn  to  an  acute  point. 
And  also  the  labrum  or  upper  lip,  an  organ  having  the 


150 


EVENINGS    AT    THE    MICROSCOPE. 


same  general  form,  but  constituting  an  imperfect  tube ;  a 
tube,  that  is  to  say,  from  which  about  a  third  of  the  peri- 
phery is  cut  away,  so  as  to  serve  as  a  sheath  for  the 
tongue,  which  ordinarily  lies  within  its  concavity. 

I  scarcely  know  whether  this 
apparatus  is  not  more  wonderfully 
delicate  than  any  we  have  ex- 
amined—  even  than  that  of  the 
Flea.  And  how  effective  it  is 
you  doubtless  well  know  ;  for 
when  the  array  of  lancets  is 
introduced  into  the  flesh,  you  are 
aware  that  a  tumour  is  left,  which, 
by  its  smart,  itching,  and  inflam- 
mation, causes  much  distress,  and 
lasts  many  hours.  This  effect  is 
probably  produced  partly  by  the 
deep  penetration  of  the  instru- 
ments— for  they  are  fully  one- 
sixth  of  an  inch  in  length,  and 
they  are  inserted  to  their  very 
kase — and  partly  by  the  injection 
of  a  poisonous  fluid,  intended,  as 
has  been  conjecturally  suggested, 
to  dilute  the  blood,  and  make  it 
more  readily  flow  up  the  capil- 
la^  tubes.  The  channel  through 
e>  labrum<  which  this  fluid  is  injected  is  pro- 
bably the  tongue,  which  you  see 
to  be  permeated  by  a  tube  containing  a  fluid ;  and  the  same 
channel  may  afford  ingress  to  the  diluted  blood. 

The  labium  does  not  enter  the  wound.  If  you  have 
ever  had  the  philosophic  patience  tb  watch  a  gnat  while 
puncturing  your  hand,  you  have  observed  that  the  knob  at 
the  end  of  the  proboscis  is  applied  to  the  skin,  and  that 
then  the  organ  bends  with  an  angle  more  and  more  acute, 


INSECTS  :    THEIR   MOUTHS. 


151 


until  at  length  it  forms  a  double  line,  being  folded  on 
itself,  so  that  the  base  is  brought  into  close  proximity  to 
the  skin.  Meanwhile  the  lancets  have  all  been  plunged 
in,  and  are  now  sunk  into  your  flesh  to  their  very  bottom, 
while  the  laUum,  which  formed  merely  the  sheath  for  the 
whole,  is  bent  up  upon  itself,  ready  again  to  assume  its 
straight  form,  as  soon  as  the  disengaged  lancets  require  its 
protection. 


TONGI'E   OF  BLOXV-FLT. 


The  tongue  of  one  of  the  common  Flies  (House-fly, 
Blow-fly,  &c.),  is  an  exquisite  microscopical  object,  from 
its  extreme  complexity  and  beauty.  You  are  familiar  with 
the  way  in  which  a  fly,  having  alighted  close  to  a  drop  of 
tea  on  the  table,  applies  to  it  a  proboscis  with  large 
dilated  extremity,  and  presently  licks  it  all  up.  You  shall 
now  see  the  curious  implement  by  which  this  is  effected. 


152  EVENINGS   AT    THE    MICROSCOPE. 

The  broad  portion  of  the  object  before  us,  forming  its 
bottom  part  bristling  with  coarse  black  hair,  is  the  front 
of  the  head  of  a  Blow-fly.  From  the  midst  of  this  projects 
a  dark  brown  mass  terminating  in  two  points,  and  in- 
closing a  narrower  and  darker  object  with  two  long  slender 
roots,  dilated  at  their  bases  ;  this  is  the  pair  of  maxilla 
altered  and  modified  into  a  kind  of  sheath  for  the  man- 
dibles. On  each  side  projects  an  elegant  club,  bristled 
with  coarse  black  hair,  and  covered  besides  with  a  coat 
of  very  minute  hairs ;  these  clubs  are  the  maxillary 
palpi. 

But  now  we  come  to  the  terminal  part,  consisting  of  a 
pair  of  lobes,  together  forming  a  rounded  triangle  in  their 
outline.  This  is  the  dilated,  and  thickened  termination  of 
the  labium,  and  is  the  instrument  by  which  the  liquids  are 
so  rapidly  sucked  up.  It  is  impossible  to  describe  this 
beautiful  structure  intelligibly ;  and,  indeed,  it  is  not  well 
understood  even  by  those  who  have  devoted  their  lives 
to  this  branch  of  natural  science.  The  principal  feature 
apparent  is  a  wide  clear  membrane,  through  which  runs 
with  admirable  symmetry  a  series  of  tubes.  These  tubes 
consist  of  four  primary  ones,  all  originating  near  the 
centre  of  the  expansion,  and  radiating  thence,  two  back- 
ward towards  the  two  lateral  angles  of  the  triangle,  and 
the  other  two  nearly  side  by  side  towards  its  point. 
From  each  of  these,  along  its  outer  side  only,  branch  off 
the  minor  tubes,  very  numerous  and  close  together,  going 
off  in  a  slightly  sinuous  line  direct  to  the  margin,  diminish- 
ing regularly  in  their  course,  and  at  their  extremities 
curving  over,  so  as  to  bring  their  open  tips  to  the  surface 
of  the  skin. 

The  construction  of  these  tubes  is  highly  interesting : 
they  are  formed,  like  the  air-pipes  (trachea),  of  a  multitude 
of  homy  rings ;  but  with  this  peculiarity,  that  the  rings 
do  not  form  a  continuous  spiral,  but  are  separate  and 
distinct,  and  are  moreover  imperfect ;  for  each  wire  (so  to 


INSECTS:  THEIB  MOUTHS.  153 

speak)  does  not  perform  a  complete  circle,  but  only  about 
two-thirds  of  a  circle,  leaving  a  blank  space ;  and  the  tips 
of  the  wires  end  alternately  in  a  fine  acute  point,  and  in  a 
rounded  fork,  like  the  prongs  of  a  pitch-fork.  It  has  been 
said  that  these  tubes  are  modified  trachea ;  but  this  fact  is 
by  no  means  obvious  to  me ;  for,  so  far  from  their  being 
connected  with  the  general  tracheal  system,  each  of  the 
four  main  tubes  originates  in  an  open  centre,  and  each 
has  an  open  extremity.  I  think  it  likely  that  they  are  so 
many  suctorial  pipes,  through  which  the  fluid  to  be  drunk 
is  drawn  up,  entering  at  their  minute  open  tips,  and  dis- 
charging itself  into  the  central  cavity  by  the  open  basal 
extremities  of  the  main  tubes. 

The  most  extraordinary  modification  of  jaws,  however, 
is  the  long  spiral  tube  which  is  ordinarily  coiled  up  under 
the  face  of  a  Butterfly  or  Moth,  with  which  it  sucks  up 
the  sweet  nectar  of  flowers.  Many  flowers  have  a  deep 
corolla,  and  most  have  the  bases  of  their  petals,  where 
the  nectar  lies,  so  far  from  the  level  of  the  surface  that 
probing  is  necessary  to  reach  it.  Bees  can  enter  tubular 
flowers,  and  lick  their  bottoms ;  and  even  blossoms  that 
are  closed,  as  the  Snapdragon,  they  know  how  to  force 
and  enter.  But  Butterflies,  with  their  wide  wings,  in- 
capable of  being  folded,  cannot  enter  flowers  bodily,  and 
therefore  a  peculiar  apparatus  is  given  them  for  stealing 
their  contents,  as  it  were,  at  the  doors. 

Nothing  is  easier  than  to  examine  this  beautiful  organ 
with  the  naked  eye ;  and  much  may  be  learned  of  its 
structure  by  means  of  a  pocket  lens.  You  may  thus  see 
in  a  moment  that  it  forms  a  flat  spiral  of  several  coils, 
like  the  mainspring  of  a  watch ;  that  it  runs  off  to  a  point, 
and  that  this  point  is  double,  for  it  is  frequently  seen 
separate  a  considerable  way  up.  Hence  you  would  pro- 
bably infer  that  the  organ  consists  of  two  equal  and  similar 
halves,  united  lengthwise.  And  so,  indeed,  it  does  ;  and 
these  halves  are  the  representatives  of  the  maxilla  or 


154  EVENINGS    AT    THE    MICKOSCOPE. 

lower  jaws  of  the  Beetle,  being  thus  greatly  developed  at 
the  expense  of  almost  all  the  other  parts.  The  upper  lip 
and  the  mandibles  are  discernible  only  in  the  form  of  three 
most  minute  plates ;  the  labial  palpi  are  large  and  promi- 
nent, those  well-haired  points  that  project  in  front  of  the 
head,  one  on  each  side  of  the  spiral.  This  spiral  form  of 
the  maxilla  is  called  antlia. 

It  is  not,  however,  very  easy  to  fix  it  in  an  extended 
condition  on  a  slip  of  glass,  so  as  that  it  shall  lie  flat 
throughout  its  whole  length,  without  injuring  the  parts 
or  so  agglutinating  them  together  that  their  structure  is 
concealed  or  distorted,  and  in  either  case  unfitted  for 
microscopical  examination.  The  specimen  which  I  have 
prepared,  from  the  mouth  of  the  Small  Garden  White 
Butterfly,  is  stretched,  and  fixed  in  balsam,  and  will,  I 
think,  show  you  the  structure  under  a  high  power  very 
well. 

Before  we  examine  it,  however,  I  will  cite  you  the 
description  of  one  of  the  most  eminent  of  microscopical 
anatomists,  Mr.  Newport.  He  considers  each  maxilla  to 
be  composed  of  an  immense  number  of  short  transverse 
muscular  rings,  which  are  convex  externally  and  concave 
internally,  the  two  connected  organs  forming  a  tube. 
Within  each  there  are  one  or  more  large  trachea  con- 
nected with  the  trachea  in  the  head.  The  inner  or  con- 
cave surface  which  forms  the  tube  is  lined  with  a  very 
smooth  membrane,  and  extends  along  the  anterior  margin 
throughout  the  whole  length  of  the  organ.  At  its  com- 
mencement at  the  tip  it  occupies  nearly  the  whole  breadth 
of  the  organ,  and  is  smaller  than  at  its  termination 
near  the  mouth,  where  the  concavity  or  groove  does  not 
occupy  more  than  about  one-third  of  the  breadth.  In 
some  species,  the  extremity  of  each  maxilla  is  furnished 
along  its  anterior  and  lateral  margin  with  a  great  number 
of  minute  papilla.  These,  in  Vanessa  Atalanta  (the  Eed 
Admiral  Butterfly),  for  instance,  form  little  barrel-shaped 


INSECTS  :    THEIB   MOUTHS.  155 

bodies,  furnished  at  the  free  end  with  three  or  more 
marginal  teeth,  and  a  larger  pointed  body  in  the  centre. 
There  are  seventy -four  of  these  in  each  maxilla,  or  half 
the  proboscis.  Mr.  Newport  regards  them  as  probably 
organs  of  taste.  There  are  also  some  curious  appendages 
arranged  along  the  inner  anterior  margin  of  each  maxilla, 
in  the  form  of  minute  hooks,  which,  when  the  proboscis  is 
extended,  serve  to  unite  the  two  halves  together,  by  the 
points  of  the  hooks  in  one  half  being  inserted  into  little 
depressions  between  the  teeth  of  the  opposite  side; 
sometimes  these  are  furnished  with  a  tooth  below  their 
tips. 

With  all  deference  to  so  respectable  an  authority,  I 
cannot  help  seeing  that  such  is  not  the  structure  of  the 
antlia  before  us.  It  is  evident  to  me  that  each  half  tube 
is  composed  of  a  membrane  stretched  upon  stiff  horny 
semi-rings,  doubtless  composed  of  chitine,  and  certainly 
not  muscular.  By  bringing  the  outline  of  the  rounded 
exterior  into  focus,  we  see  that  these  rings  form  sharp 
ridges;  and  by  tracing  them  onwards  to  the  attenuated 
extremity  of  the  organ,  we  see  them  gradually  give  way 
to  transverse  lines  of  interrupted  ridgy  warts  upon  the 
outside  of  the  membrane.  The  true  muscles  appear  to  be 
indicated  by  those  oblique  lines  and  bands  that  are  seen 
in  the  interior,  beneath  the  horny  rings. 

This  specimen  shows  very  distinctly  that  the  two  sides 
are  but  semi-tubular,  and  as  one  pair  of  the  opposing 
edges  are  open  at  each  extremity,  and  the  other  pair 
separate  throughout,  we  are  able  to  discern  very  clearly 
the  array  of  hooks,  by  which  the  edges  are  united  at  the 
will  of  the  animal.  No  trace  of  the  curious  little  pointed 
barrel- shaped  papilla  is  found  here,  but  I  have  seen  it  in 
other  examples. 

It  seems  highly  probable,  from  the  observations  of  the 
excellent  anatomist  just  named,  that  the  exhaustion  of  the 
nectar  of  a  flower,  which  is  effected  with  great  rapidity 


156 


EVENINGS   AT    THE    MICROSCOPE. 


THE  SUCKER  OF  A  BUTTERFLY. 

A  small  portion  of  one  half- 
cylinder. 


and  completeness,  is  a  process  dependent  on  respiration, 
and  connected  with  the  air-pipe  that  permeates  each  divi- 
sion of  the  sucker.* 

It  will  not  be  a  very  violent 
transition  if  from  the  sucking- 
pump  of  the  Butterfly  I  carry  you 
to  the  silk- spinner  of  the  Cater- 
pillar. Here  I  have  a  Silkworm 
in  the  act  of  commencing  its 
cocoon ;  by  inclosing  which  in  this 
glass  tube  we  shall  conveniently 
have  the  insect  at  command,  and 
shall  be  able  to  view  the  process 
under  a  low  magnifying  power  and- 
reflected  light.  Now  the  grey  face 
of  the  worm  is  presented  to  us  ; 
and  we  can  see,  below  the  edge 
of  the  head- shield,  a  short  broad 

upper  lip,  forming  two  blunt  points.  Below  this  is  the 
pair  of  strong  brown  mandibles,  convex  outwardly  and 
concave  inwardly,  each  cut  at  its  broad  biting  edge  into 
several  teeth.  Below  these  are  two  little  points  which 
represent  the  maxilla,  and  between  them  a  blunt  rounded 
knob,  which  is  the  lower  lip  (labium). 

You  may  also  see  on  each  cheek,  close  to  the  base  of 
the  mandible,  a  little  pit,  out  of  which  rises  a  short 
columnar  organ  tipped  with  two  bristles  ;  these  columns 
are  the  incipient  antenna.  Outside  them  you  may  dis- 
cern, on  each  cheek,  a  series  of  six  globes  of  glass  (so 
they  appear)  set  in  the  substance  of  the  skin} — five 
forming  a  semicircle,  and  one  in  the  centre ;  these  are 

*  Mr.  Darwin,  in  his  admirable  work  On  the  Fertilisation  of  Orchids, 
p.  33  et  seq.,  has  shown  that  the  tubular  proboscis  of  Lepidoptera, 
while  used  by  the  insect  solely  for  the  collection  of  nectar,  is  indirectly 
and  unintentionally  used  for  the  transferring  of  pollen-grains  from 
flower  to  flower ;  and  thus  becomes  a  most  important  agent  in  the  pro- 
pagation of  plants.  (See  his  remarkable  figure  on  p.  37  op.  cit.) 


INSECTS:    THEIR  MOUTHS.  157 

"  the  windows  at  which  the  [silkworm's]  soul  looks 
through" — provided  he  has  any  soul — in  prosaic  par- 
lance, his  eyes. 

Now,  having  thus  introduced  the  several  members  of 
our  useful  friend's  physiognomy  to  you,  let  me  call  your 
attention  to  a  fleshy  wart  just  beneath  the  lower  lip,  and 
midway  between  the  bases  of  the  two  fore  legs.  This 
wart  terminates  in  a  horny  point  not  unlike  a  bird's  beak, 
which  is  perforated,  and  from  the  tip  of  which  the  glisten- 
ing yellow  filament  of  silk  is  ever  drawn  out,  as  the  cater- 
pillar throws  his  head  from  side  to  side.  This  pointed 
wart  is  the  spinning  organ ;  and  the  thread  of  silk  is, 
as  it  issues  from  the  orifice,  a  fluid  gum,  which  hardens 
immediately  on  its  exposure  to  the  air.  The  silk-gum  is 
secreted  by  the  caterpillar  in  two  long  blind  tubes,  which 
lie  twisted  and  coiled  in  the  interior  of  the  body,  occupy- 
ing nearly  the  whole  space,  except  that  which  is  taken  up 
by  the  great  digestive  canal.  These  become  very  slender 
as  they  approach  the  head,  and  at  length  terminate  in  a 
reservoir,  which  opens  by  the  little  pointed  wart  which  you 
have  just  seen. 

Many  caterpillars  are  able  to  suspend  themselves  at 
pleasure  by  means  of  the  thread  which  they  are  spinning, 
lengthening  it  and  "  stopping  it  off,"  at  will.  This  latter 
operation  they  perform  (though  they  cannot  recal  the 
thread  when  once  it  has  issued)  by  means  of  an  angular 
point  formed  by  the  two  slender  tubes  at  their  junction  in 
the  reservoir  ;  thus  compressing  the  thread  of  gum,  and 
so  preventing  any  more  from  issuing.  The  gum  is  per- 
fectly colourless  in  the  reservoir,  but  as  it  issues  forth 
becomes  coated  with  a  varnish,  which  is  secreted  in  the 
same  organ,  and  which  is  poured  out  at  the  same  tune. 
In  the  case  of  the  common  Silkworm,  this  varnish  imparts 
to  the  silk  that  brilliant  yellow  hue  which  it  generally 
possesses,  and  which,  as  the  varnish  is  soluble,  can  be 
easily  discharged  from  it  in  the  manufacture. 


158  EVENINGS    AT    THE    MICROSCOPE. 


CHAPTER  X. 

INSECTS  :    THEIR    EARS    AND    EYES. 

A  VERY  wide  field  of  observation,  and  one  easily  culti- 
vated, is  presented  by  the  organs  of  sense  in  the  Insect 
races,  and  in  particular  by  those  curious  jointed  threads 
which  proceed  from  the  front  or  sides  of  the  head,  and 
which  are  technically  called  antenna.  These  may  some- 
times be  confounded  with  the  jmlpi,  examples  of  which 
organs  we  have  been  lately  looking  at ;  for  in  a  carnivor- 
ous Beetle,  for  instance,  both  palpi  and  antenna  are 
formed  of  a  number  of  oblong,  polished  hard  joints,  set 
end  to  end,  like  beads  on  a  necklace.  And  it  is  probable 
there  may  be  as  much  that  is  alike  in  the  function  as  in 
the  form  of  these  two  sets  of  appendages ;  that  both  are 
the  seats  of  some  very  delicate  perceptive  faculty  allied  to 
touch,  but  of  which  we  cannot,  from  ignorance,  speak 
very  definitely.  It  is  likely,  indeed,  that  sensations  of  a 
very  variable  character  are  felt  by  them,  according  to  their 
form,  the  degree  of  their  development,  and  the  habits  of 
the  species. 

It  is  not  impossible,  judging  from  the  very  great  diver- 
sity which  we  find  in  the  form  and  structure  of  these  and 
similar  organs  in  this  immense  class  of  beings,  compared 
with  the  uniformity  that  prevails  in  the  organs  of  sense 
bestowed  on  ourselves  and  other  vertebrate  animals, — that 
a  far  wider  sphere  of  perception  is  open  to  them  than  to 
us.  Perhaps  conditions  that  are  perceptible  to  us  only  by 
the  aid  of  the  most  delicate  instruments  of  modern  science 
may  be  perceptible  to  their  acute  faculties,  and  may 


INSECTS  :    THEIR  EAES    AND  EYES.  159 

govern  their  instincts  and  actions.  Among  such  we  may 
mention,  conjecturally,  the  comparative  moisture  or  dry- 
ness  of  the  atmosphere,  delicate  changes  in  its  tempera- 
ture, in  its  density,  the  presence  of  gasepus  exhalations, 
the  proximity  of  solid  bodies  indicated  by  subtle  vibrations 
of  the  air,  the  height  above  the  earth  at  which  flight  is 
performed,  measured  barometrically,  the  various  electrical 
conditions  of  the  atmosphere;  and  perhaps  many  other 
physical  qualities  which  cannot  be  classed  under  sight, 
sound,  smell,  taste,  or  touch,  and  which  may  be  alto- 
gether imperceptible,  and  therefore  altogether  incon- 
ceivable, by  us.  It  is  probable,  however,  that  the 
antenna  are  the  organs  in  which  the  sense  of  hearing  is 
specially  seated ;  a  conclusion  which  has  long  been 
conjecturally  held,  and  which  is  confirmed  by  some  obser- 
vations recently  made  on  the  analogous  organs  in  the 
Crustacea,  which  I  will  allude  to  more  particularly  pre- 
sently. 

The  forms  which  are  assumed  by  the  antenna  of  Insects 
are  very  various  ;  and  I  can  bring  before  you  only  a  very 
small  selection  out  of  the  mass.  One  of  the  most  simple 
forms  is  that  found  in  many  Beetles,  as  in  this  Carabus, 
for  example.  Here,  each  antenna  is  composed  of  eleven 
joints,  almost  exactly  alike  and  symmetrical,  each  joint  a 
horny  body  of  apparently  a  long-oval  shape,  polished  on 
the  surface,  but  not  smooth,  because  covered  with  minute 
depressed  lines,  and  clothed  with  shaggy  hair.  There  is, 
however,  a  slight  illusion  in  the  appearance  :  it  seems  as 
if  the  dividing  point  of  the  joints  were,  as  I  have  just 
said,  at  the  termination  of  the  oval,  but  when  we  look 
closely  we  see  that  the  summit  of  each  oval  is,  as  it  were, 
cut  off  by  a  line,  and  by  comparing  the  basal  joints  with 
the  others,  we  see  that  this  line  is  the  real  division,  that 
the  summit  of  the  oval  really  forms  the  bottom  of  the 
succeeding  joint,  and  that  the  constricted  part  is  no 
articulation  at  all.  The  first,  or  basal  joint  (called  the 


160  EVENINGS    AT    THE    MICROSCOPE. 

scapus],  and  the  second  (called  the  pedicella),  differ  in 
form  from  the  rest  here  but  slightly,  but  often  consider- 
ably. The  whole  of  the  remaining  joints  are  together 
termed  the  clavola. 

You  may  see  a  considerable  variety  of  figure  and  of 
aspect  generally  in  this  tiny  Weevil,  which  may  be  accepted 
as  a  representative  of  a  great  family  of  Beetles,  the  Cur- 
cidionidcB.  The  manner  of  their  insertion  strikes  us  at 
first  sight  as  peculiar,  as  is  in  fact  the  aspect  of  the  whole 
head.  Instead  of  a  thick  substantial  solid  front,  with 
powerful  widely-gaping  jaws,  such  as  we  saw  in  the 
Carabs,  a  long  rod-like  proboscis  here  projects  from 
between  the  eyes,  as  long  as  the  whole  animal,  curving 
downwards,  and  carrying  at  its  very  extremity  a  minute 
mouth,  with  all  the  proper  apparatus  of  lips,  jaws,  and 
palpi.  Moreover,  the  antenna  are  planted  on  the  two 
sides  of  this  beak,  about  its  mid-length  ;  and  they  are 
curiously  elbowed,  each  projecting  horizontally  at  a  right 
angle  to  the  beak  for  a  considerable  distance,  and  then 
with  a  sharp  angle  becoming  parallel  to  it  for  the  re- 
mainder of  their  length.  So  that,  supposing  the  terminal 
half  of  the  beak  to  be  broken  off  just  behind  the  insertion 
of  the  antenna,  the  whole  would  compose  the  letter  T. 
Now,  the  first  bend  of  this  angle  is  composed  of  a  single 
joint,  the  scapus,  which  is,  in  this  family,  greatly  length- 
ened ;  and  then  the  two  or  three  final  joints  are  much 
thicker  than  all  the  others,  and  are  as  it  were  fused 
together  into  a  large  oval  knob,  called  the  club. 

Now,  a  word  or  two  in  explanation  of  this  very  singular 
form  of  head  and  head-organs.  The  larva  or  grub  stage 
of  these  insects  is  destined  to  be  passed  in  the  interior  of 
fruits  and  seeds;  the  individual  which  we  have  been 
examining  (Balaninus  nucwni)  was  born  one  morning  in 
August,  in  the  interior  of  a  hazel-nut.  Its  parent  had 
chosen  a  suitable  nut,  just  then  when  it  was  set  for  fruit 
and  as  yet  green  and  soft ;  and  had  with  her  proboscis,  or 


INSECTS  :    THEIR    EAES   AND    EYES.  161 

rather  with  her  jaws  at  its  tip,  as  with  a  gimlet,  bored  a 
tiny  hole  through  the  yielding  shell  into  the  very  interior ; 
then  turning  round,  and  inserting  the  extremity  of  her 
abdomen,  with  its  ovipositor,  she  had  shot  an  egg  into  this 
dark  cavity.  The  juices  poured  forth  at  the  wound  soon 
healed  the  orifice  ;  the  nut  grew ;  and  presently  the  egg 
became  a  little  white  grub.  He  then  rioted  in  plenty ; 
prolonged  his  darkling  feast 

"  From  night  to  morn,  from  morn  to  dewy  eve ; " 

— 'twas  all  "  dewy  eve  "  to  him,  by  the  way,  for  no  ray 
of  light  saw  he,  till  that  prosperous  condition  of  existence 
was  done.  No  wonder  he  grew  fat ;  and  fat  those  rogues 
of  nut-weevils  always  are,  as  you  well  know.  Well,  when 
the  nut  fell,  in  October,  the  kernel  was  all  gone,  com- 
pletely devoured,  and  our  little  highway  robber  was  ready 
for  his  winter  sleep  ;  he  gnawed  a  fresh  hole  through  the 
now  hard  shell,  made  his  way  out,  and  immediately  bur- 
rowed into  the  earth,  where  he  lay  till  June  ;  then  became 
a  pupa,  and  emerged  just  what  you  see  him,  a  long- 
snouted  beetle  like  his  mother,  in  the  beginning  of 
August. 

Such  is  his  "  short  eventful  history ; "  and  you  now 
see  that  the  long  beak  is  formed  entirely  with  reference 
to  this  economy :  it  is  an  auger,  fitted  to  bore  holes  into 
shell-fruits,  through  their  envelopes,  for  the  reception  of 
eggs. 

There  is  a  very  extensive  family  of  Beetles  known  as 
Lamellicornes,  because  the  antennal  joints  are  singularly 
flattened,  and  applied  one  over  the  other,  like  the  leaves 
of  a  book  (lamella,  a  leaf).  Here  is  a  very  common  little 
Chafer  found  on  the  droppings  in  pastures  (Aphodius 
fimetarius),  in  which  the  last  three  joints,  constituting  the 
club  of  the  antenna,  are  of  an  ovate  form,  and  flattened, 
so  as  to  lie  one  on  another  quite  close,  like  three  oval 

M 


162  EVENINGS   AT    THE   MICROSCOPE. 

cakes  ;  and  being  connected  only  at  one  end  of  the  long 
axis,  they  open  and  shut  at  the  pleasure  of  the  animal,  like 
a  long  pocket  memorandum-book  of  three  leaves. 

But  this  structure  is  seen  to  still  greater  advantage  in 
the  much  larger  Cockchafer,  so  abundant  in  May  in  some 
seasons.  For  here  the  joints  composing  the  club  are 
much  more  numerous  (seven  in  the  male,  six  in  the 
female),  and  they  are  proportionally  longer  and  thinner, 
and  therefore  more  leaf-like.  The  insect  widely  expands 
them,  evidently  to  receive  impressions  from  the  atmo- 


AKTENNA  OF   COCKCHAFER. 


sphere  ;  when  alarmed,  they  are  closed  and  withdrawn 
beneath  the  shield  of  the  head,  but  on  the  first  essay 
towards  escape,  or  any  kind  of  forward  movement,  the 
leaves  are  widely  opened,  and  then,  after  an  instant's 
pause  to  test  the  perceptions  on  the  sensorium,  away  it 
travels. 

In  some  Beetles  each  joint  of  the  series  has  one  of  its 
outer  angles  more  developed  than  the  other,  and  so  pro- 
duced as  to  make,  with  the  rest  of  the  joints,  a  saw-like 
edge ;  you  may  see  an  example  in  this  Click-beetle  or 


INSECTS  I    THEIR    EARS    AND    EYES.  163 

Skipjack  (Elater),  but  many  members  of  the  same  family 
show  the  same  structure  in  a  far  higher  degree,  the  angle 
being  drawn  out  into  a  long  slender  rod,  which  (with  its 
fellows)  imparts  to  the  antenna  the  appearance  of  a 
comb. 

But  much  more  curious  and  beautiful  are  the  antennae 
of  many  moths,  which  often  resemble  feathers,  particularly 
in  the  group  Bombycina,  of  which  the  Silkworm  is  an 
example ;  and  in  the  male  sex,  which  displays  this  struc- 
ture more  than  the  female.  But  I  will  show  you  a  native 
example. 

This  is  the  antenna  of  a  large  and  handsome,  and  not 
at  all  uncommon  moth — the  Oak  Egger  (Lasiocampa 
quercus).  It  consists  of  about  seventy  joints,  so  nearly 
alike  in  size  and  outline,  that  the  whole  forms  an  almost 
straight  rod,  slightly  tapering  to  the  tip.  Each  joint, 
however,  sends  forth  two  long  straight  branches,  so  dis- 
posed that  the  pair  make  a  very  acute  angle,  and  the 
whole  double  series  of  seventy  on  each  side,  form  a  deep 
narrow  groove.  These  two  series  of  branches,  being  per- 
fectly regular  and  symmetrical,  impart  to  the  antenna  the 
aspect  of  exquisite  feathers. 

It  is,  however,  when  we  examine  the  elements  of  this 
structure  in  detail,  using  moderately  high  powers  of 
enlargement,  that  we  are  struck  with  the  elaborateness  of 
the  workmanship  bestowed  upon  them.  Each  of  the 
lateral  branches  is  a  straight  rod,  thick  at  its  origin, 
whence  it  tapers  to  a  little  beyond  its  middle,  and  then 
thickens  again  to  its  tip.  Here  two  horny  spines  project 
from  it  obliquely,  one  much  stouter  than  the  other,  at 
such  an  angle  as  nearly  to  touch  the  tip  of  the  succeeding 
branch. 

Besides  this,  each  branch  is  surrounded  throughout  its 

length  with  a  series  of  short  stiff  bristles,  very  close-set, 

projecting    horizontally   (to  the  plane  of  the  axis  of  the 

branch),  and  bent  upwards  at  the  end  candelabrum-fashion. 

M  2 


164  EVENINGS    AT    THE    MICROSCOPE. 

The  mode  in  which  they  are  arranged  is  in  a  short  spiral, 
which  makes  about  forty-five  whorls  or  turns  about  the 
axis  ;  at  least  in  the  branches  which  are  situated  about 
the  middle  of  the  antenna ;  for  these  diminish  in  length 
towards  the  extremity,  bringing  the  feather  to  a  rather 
abrupt  point. 

The  entire  surface  of  the  branch  gleams  under  reflected 
light  with  metallic  hues,  chiefly  yellows  and  bronzy 
greens  ;  which  appear  to  depend  on  very  minute  and 
closely-applied  scales  that  overlap  each  other.  The  main 
stem  of  the  feather, — that  is,  the  primary  rod  or  axis, — is 
somewhat  sparsely  clothed  with  scales  of  another  kind, 
thin,  oblong,  flat  plates,  notched  at  the  end,  and  very 
slightly  attached  by  means  of  a  minute  stem  at  the  base, — 
the  common  clothing-scales  of  the  Lepidoptera, — speci- 
mens of  which  we  have  before  examined. 


PORTION  OF  ANTENNA  OF  OAK  EGGER  MOTH. 


We  may  acquire  some  glimpse  of  a  notion  why  this 
remarkable  development  of  antennas  is  bestowed  upon  the 
male  sex  of  this  moth,  by  an  acquaintance  with  its  habits. 
It  has  long  been  a  practice  with  entomologists,  when  they 
have  reared  a  female  moth  from  the  chrysalis,  to  avail 
themselves  of  the  instincts  of  the  species  to  capture  the 


INSECTS:  THEIR  EARS  AND  EYES.  165 

male.  This  sex  has  an  extraordinary  power  of  discover- 
ing the  female  at  immense  distances,  even  though  she  be 
perfectly  concealed  ;  and  will  crowd  towards  her  from  all 
quarters,  entering  into  houses,  beating  at  windows,  and 
even  descending  chimneys,  to  come  at  the  dear  object  of 
their  solicitude.  Collectors  call  this  mode  of  procuring 
the  male  "  sembling,"  that  is,  " assembling"  because  the 
insects  of  this  sex  assemble  at  one  point.  It  cannot  be 
practised  with  all  insects,  nor  even  with  all  moths ;  with 
this  family,  Bombycida,  it  is  in  general  successful ;  and  of 
these,  none  is  more  celebrated  for  the  habit  than  the  Oak 
Egger.  The  very  individual  whose  antenna  has  furnished 
us  with  this  observation  was  taken  in  this  way  ;  for  having 
bred  a  female  of  this  species  the  evening  before  last,  I  put 
her  into  a  basket  in  my  parlour.  One  male,  the  same 
evening,  came  dashing  into  the  kitchen ;  but  yesterday, 
soon  after  noon,  in  the  hot  sunshine  of  August,  no  fewer 
than  four  more  males  came  rapidly  in  succession  to  the 
parlour  window,  which  was  a  little  open,  and,  after  beating 
about  the  panes  a  few  minutes,  found  their  way  in,  and 
made  straightway  for  the  basket,  totally  regardless  of  their 
own  liberty. 

It  must  be  manifest  to  you  that  some  extraordinary 
sense  is  bestowed  on  these  moths,  or  else  some  ordinary 
and  well-known  sense  in  extraordinary  development.  It 
may  be  smell ;  it  may  be  hearing  ;  but  neither  odour  nor 
sound,  perceptible  by  our  dull  faculties,  is  given  forth  by 
the  females ;  the  emanation  is  far  too  subtle  to  produce 
any  vibrations  on  our  sensorium,  and  yet  sufficiently 
potent,  and  widely  diffused,  to  call  these  males  from  their 
distant  retreats  in  the  hedges  and  woods.  I  think  it 
highly  probable  that  the  great  increase  of  surface  given  to 
the  antennae  by  the  plumose  ramification  we  have  been 
observing,  is  connected  with  the  faculty;  perhaps  every 
bristle  of  the  spiral  whorls  is  a  perceptive  organ,  con- 
structed to  vibrate  with  the  tender  undulations  that  circle 


166  EVENINGS    AT   THE    MICROSCOPE. 

far  and  wide  from  the  new-born  female.  Surely  the  ways 
of  God  in  creation  are  "  past  finding  out." 

The  male  Gnat  presents  in  its  antennas  a  pair  of  plumes 
of  equal  beauty,  but  of  a  totally  different  character. 
The  pattern  here  is  one  of  exceeding  lightness  and  grace, 
as  you  may  see  in  this  specimen.  Each  antenna  is  essen- 
tially a  very  slender  cylindrical  stem  of  many  joints  (about 
fourteen) ;  at  each  joint  springs  out  a  whorl  of  fine  hairs 
of  great  length  and  delicacy,  which  radiate  in  various 
directions  (not,  however,  forming  a  complete  circle), 
curving  upward  like  the  outline  of  a  saucer,  supposing 
the  stem  to  be  inserted  into  its  centre.  The  length  of 
these  hairs  is  so  great,  that  the  diameter  of  their  sweep 
equals,  if  it  does  not  exceed,  the  whole  length  of  the 
antenna. 

In  the  tribe  of  two- winged  insects,  which  we  term  par 
excellence  Flies  (MuscadcB),  the  antennae  are  of  peculiar 
structure.  The  common  House-fly  shall  give  us  a  good 
example.  Here,  in  front  of  the  head,  is  a  shell-like  con- 
cavity, divided  into  two  by  a  central  ridge.  Just  at  the 
summit  of  this  project  the  two  antennas,  originating  close 
together,  and  diverging  as  they  proceed.  Each  antenna 
consists  of  three  joints,  of  which  the  first  is  very  minute, 
the  second  is  a  reversed  cone,  and  the  third,  which  is 
large,  thick,  and  ovate,  is  bent  abruptly  downwards  imme- 
diately in  front  of  the  concavity.  From  the  upper  part 
of  this  third  joint  projects  obliquely  a  stiff  bristle  or  style, 
which  tapers  to  a  fine  point.  It  is  densely  hairy  through- 
out ;  and  is  moreover  beset  with  longer  hairs,  on  two  oppo- 
site sides,  which  decrease  regularly  in  length  from  the  base, 
making  a  wide  and  pointed  plume. 

Such  are  a  few  examples  of  what  are  presumed  to  be 
the  ears  of  Insects ;  let  us  now  turn  our  attention  to  their 
eyes.  And  we  can  scarcely  select  a  more  brilliant,  or  a 
larger  example,  than  is  presented  by  this  fine  Dragon-fly 
(jEshna),  which  I  just  now  caught  as  it  was  hawking  to 


INSECTS  :    THEIR  EARS   AND  EYES.  167 

and  fro  in  my  garden.  How  gorgeously  beautiful  are 
these  two  great  hemispheres  that  almost  compose  the 
head,  each  shining  with  a  soft  satiny  lustre  of  azure  hue, 
surrounded  by  olive-green,  and  marked  with  undefined 
black  spots,  which  change  their  place  as  you  move  the 
insect  round ! 

Each  of  these  hemispheres  is  a  compound  eye.  I  put 
the  insect  in  the  stage -forceps,  and  bring  a  low  power  to 
bear  upon  it  with  reflected  light.  You  see  an  infinite 
number  of  hexagons,  of  the  most  accurate  symmetry  and 
regularity  of  arrangement.  Into  those  which  are  in  the 
centre  of  the  field  of  view,  the  eye  can  penetrate  far 
down,  and  you  perceive  that  they  are  tubes ;  of  those 
which  recede  from  the  centre,  you  discern  more  and  more 
of  the  sides ;  while,  by  delicate  adjustment  of  the  focus, 
you  can  see  that  each  tube  is  not  open,  but  is  covered  with 
a  convex  arch  of  some  glassy  matter,  polished  and  trans- 
parent as  crystal.  There  are,  according  to  the  com- 
putations of  accurate  naturalists,  not  fewer  than  24,000 
of  these  convex  lenses  in  the  two  eyes  of  such  a  large 
species  of  Dragon-fly  as  this. 

Every  one  of  these  24,000  bodies  represents  a  perfect 
eye ;  every  one  is  furnished  with  all  the  apparatus  and 
combinations  requisite  for  distinct  vision  ;  and  there  is  no 
doubt  that  the  Dragon-fly  looks  through  them  all.  In 
order  to  explain  this,  I  must  enter  into  a  little  technical 
explanation  of  the  anatomy  of  the  organs,  as  they  have 
been  demonstrated  by  careful  dissection. 

The  glassy  convex  plate  or  facet  in  front  of  each 
hexagon  is  a  cornea  or  corneule,  as  it  has  been  called. 
Behind  each  cornea,  instead  of  a  crystalline  lens,  there 
descends  a  slender  transparent  pyramid,  whose  base  is 
the  cornea,  and  whose  apex  points  towards  the  interior, 
where  it  is  received  and  embraced  by  a  translucent  cup, 
answering  to  the  vitreous  humour.  This,  in  its  turn,  is 
surrounded  by  another  cup,  formed  by  the  expansion  of  a 


168  EVENINGS    AT    THE    MICROSCOPE. 

nervous  filament  arising  from  the  ganglion,  or  knot,  on 
the  extremity  of  the  optic  nerve,  a  short  distance  from 
the  brain.  Each  lens-like  pyramid,  with  its  vitreous  cup 
and  nervous  filament,  is  completely  'surrounded  and 
isolated  by  a  coat  (the  choroid)  of  dark  pigment,  except 
that  there  is  a  minute  orifice  or  pupil  behind  the  cornea, 
where  the  rays  of  light  enter  the  pyramid,  and  one  at  the 
apex  of  the  latter,  where  they  reach  the  fibres  of  the  optic 
nerve. 

Each  cornea  is  a  lens  with  a  perfect  magnifying  power, 
as  has  been  proved  by  separating  the  entire  compound 
eye  by  maceration,  and  then  drying  it,  flattened  out  by 
pressure,  on  a  slip  of  glass.  When  this  preparation  was 
placed  under  the  microscope,  on  any  small  object,  as  the 
points  of  a  forceps,  being  interposed  between  the  mirror 
and  the  stage,  its  image  was  distinctly  seen,  on  a  proper 
adjustment  of  the  focus  of  the  microscope,  in  every  one 
of  the  lenses  whose  line  of  axis  admitted  of  it.  The  focus 
of  each  cornea  has  been  ascertained  by  similar  experi- 
ments to  be  exactly  equal  to  the  length  of  the  pyramid 
behind  it,  so  that  the  image  produced  by  the  rays  of  light 
proceeding  from  any  external  object,  and  refracted  by  the 
convex  cornea,  will  fall  accurately  upon  the  sensitive 
termination  of  the  optic  nerve-filament  there  placed  to 
receive  it. 

The  rays  which  pass  through  the  several  pyramids  are 
prevented  from  mingling  with  each  other  by  the  isolating 
sheath  of  dark  pigment ;  and  no  rays,  except  those  which 
pass  along  the  axis  of  each  pyramid,  can  reach  the  optic 
nerve ;  all  the  rest  being  absorbed  in  the  pigment  of  the 
sides.  Hence  it  is  evident,  that  as  no  two  corner  on  the 
rounded  surface  of  the  compound  eye  can  have  the  same 
axis,  no  two  can  transmit  a  ray  of  light  from  the  very 
same  point  of  any  object  looked  at ;  while,  as  each  of  the 
composite  eyes  is  immovable,  except  as  the  whole  head 
moves,  the  combined  action  of  the  whole  24,000  lenses 


INSECTS:  THEIB  EABS  AND  EYES.  169 

can  present  to  the  sensorimn  but  the  idea  of  a  single, 
undistorted,  unconfused  object,  probably  on  somewhat  of 
the  same  principle  by  which  the  convergence  of  the  rays 
of  light  entering  our  two  eyes  gives  us  but  a  single  stereo- 
scopic picture. 

The  soft  blue  colour  of  this  Dragon-fly's  eyes, — as  also 
the  rich  golden  reflections  seen  on  the  eyes  of  other 
insects,  as  the  Whame-flies,  and  many  other  Diptera, — 
is  not  produced  by  the  pigment  which  I  have  alluded  to, 
but  is  a  prismatic  reflection  from  the  cornea. 

You  would  suppose  that,  having  24,000  eyes,  the 
Dragon-fly  was  pretty  well  furnished  with  organs  of  vision, 
and  surely  would  need  no  more ;  but  you  would  be 
mistaken.  It  has  three  other  eyes  of  quite  another 
character. 

If  you  look  at  the  commissure  or  line  of  junction  of  the 
two  compound  eyes  on  the  summit  of  the  head,  you  will 
see,  just  in  front  of  the  point  where  they  separate  and 
their  front  outlines  diverge,  a  minute  crescent-shaped 
cushion  of  a  pale-green  colour,  at  each  angle  of  which  is 
a  minute  antenna.  Close  to  the  base  of  each  antenna 
there  is  set  in  the  black  skin  of  the  head  that  divides  the 
green  crescent  from  the  compound  eyes,  a  globose, 
polished  knob  of  crystal-like  substance,  much  like  the 
"  bull's  eyes  "  that  are  set  in  a  ship's  deck  to  enlighten 
the  side-cabins.  On  the  front  side  of  the  cushion  there 
is  a  third  similar  glassy  sphere,  but  much  larger  than  the 
two  lateral  ones.  What  are  these  ? 

They  are  eyes,  in  no  important  respect  differing  from 
the  individuals  which  compose  the  compound  masses, 
except  that  they  are  isolated.  The  shining  glassy  sphere 
is  a  cornea  of  hard  transparent  substance,  behind  which 
is  situated  a  spherical  lens,  lodged  in  a  kind  of  cup  formed 
by  an  expansion  of  the  optic  nerve,  and  which  is  sur- 
rounded by  a  coloured  pigment-layer. 

You  may  study  these  simple  eyes,  or  stemmata  as  they 


170  EVENINGS   AT    THE    MICROSCOPE. 

are  called,  in  many  other  insects,  though  they  are  not  so 
universally  present  as  the  compound  eyes.  On  the  fore- 
head of  the  Honey-bee  they  are  well  seen,  as  three  black 
shining  globules,  placed,  as  in  the  Dragon-fly,  in  a 
triangle. 

It  is  reasonable  to  presume  that  some  difference,  im- 
portant to  the  insect,  exists  between  the  perceptions 
obtained  by  means  of  the  simple,  and  those  obtained  by 
means  of  the  compound,  eyes  ;  but  what  is  the  nature  of 
the  difference  is  certainly  not  known,  and  probably  could 
not  be  imagined  by  us,  who  know  only  one  kind  of  vision. 


CRABS   AND    SHRIMPS.  171 


CHAPTER  XI. 

CRABS     AND     SHRIMPS. 

0 

IT  is  always  interesting  to  trace  the  varied  forms  and  con- 
ditions under  which  any  particular  function  is  performed ; 
and  particularly  to  mark,  in  creatures  very  remote  from 
us  in  the  scale  of  being,  the  organs  devoted  to  the  senses 
which  are  so  requisite  to  our  own  comfort.  We  have 
already  seen  some  of  these  diversities  in  examples  taken 
from  the  classes  Mollusca  and  Insects;  and  will  now 
examine  some  more,  as  they  appear  in  the  Crustacea. 

If  you  look  at  the  head  of  a  Crab,  a  Lobster,  or  a 
Prawn,  you  will  see  that  it  is  furnished,  like  that  of  In- 
sects, with  jointed  antennae  ;  but,  whereas  in  insects  there 
is  never  more  than  a  single  pair,  in  the  creatures  of  which 
I  am  speaking  there  are  two  pairs.  In  the  Prawn  you 
may  suppose,  at  first  sight,  that  there  are  four  pairs ;  but 
that  is  because  the  internal  antennae  terminate  each  in 
three  many-jointed  bristles,  in  structure  and  appearance 
exactly  like  the  bristles  of  the  outer  pair,  two  of  the  three 
being  nearly  as  long  as  the  outer,  while  the  third  is  short. 
In  the  Lobster,  the  internal  are  two-bristled,  both  bristles 
rather  short,  while  the  external  are  very  long.  In  the 
Flat-crabs  each  pair  is  simple,  the  inner  minute,  the  outer 
long.  In  the  great  Eatable  Crab  each  pair  is  very  small, 
and  they  are  dissimilar. 

-  Now,  taking  the  last-named  animal  as  the  representative 
of  his  class,  let  us  examine  one  of  his  inner  antennae  first. 
It  consists  of  a  jointed  stem  and  a  terminating  bristle; 
the  latter  furnished  with  small  hairs  common  to  the 


172  EVENINGS   AT    THE    MIOKOSCOPE. 

general  surface  of  the  body,  and  with  long,  delicate,  mem- 
branous filaments  (setts,  often  improperly  called  cilia}, 
which  are  larger  and  much  more  delicate  in  structure 
than  the  ordinary  hairs. 

The  basal  joint  is  greatly  enlarged  :  if  it  be  carefully 
removed  from  its  connexion  with  the  head,  and  broken 
open,  it  will  be  found  to  inclose  in  its  cavity  a  still  smaller 
chamber,  with  calcareous  walls  of  a  much  more  delicate 
character  than  the  outer  walls.  This  internal  cell  is  con- 
sidered by  Mr.  Spence  Bate  to  be  a  cochlea,*  from  its 
analogy,  both  in  structure  and  supposed  use,  to  the  organ 
so  named  in  the  internal  ear  of  man  and  other  vertebrate 
animals.  It  is  situated,  as  has  been  said,  in  the  cavity  of 
the  basal  joint  of  the  internal  antenna,  and  is  attached  to 
the  interior  surface  of  its  wall  farthest  from  the  median 
line  of  the  Crab.  It  has  a  tendency  to  a  spiral  form,  but 
does  not  pass  beyond  the  limits  of  a  single  convolution. 

If  this  interior  cell  does  indeed  represent  the  cochlea 
of  more  highly-constructed  ears,  to  which  it  bears  some 
resemblance  both  in  form  and  structure,  then  it  seems  to 
identify,  beyond  dispute,  these  inner  or  upper  antennae  as 
the  organs  of  hearing. 

Now  with  this  conclusion  agrees  well  the  manner  in 
which  the  living  animal  makes  use  of  the  organs  in  ques- 
tion. The  Crab  always  carries 
them  erect  and  elevated ;  and 
is  incessantly  striking  the  water 
with  them,  with  a  very  peculiar 
jerking  action,  now  and  then 
vibrating,  and,  as  it  has  been 
called/ 'twiddling "them.  These 

EAR  OF  CRAB  FROM  BEHIND,      antennae,   therefore,  appear  to 
be  always  on  the  watch  :    let 

*  Cochlea,  the  Latin  for  Snail-shell,  is  the  name  given  to  one  of 
the  cavities  of  the  ear,  from  its  resemblance  to  the  interior  of  a  snail- 
shell. 


e-  m 

.  •      '  m?* 


CBABS    AND    SHRIMPS.  173 

the  animal  be  at  rest,  let  it  be  feeding,  no  matter,  the 
inner  antennae  are  ever  elevated  and  on  constant  guard. 

The  lengthened  and  delicate  set®  with  which  they  are 
furnished  are,  moreover,  peculiarly  adapted  to  receive  and 
convey  the  most  minute  vibratory  sensations  from  the 
medium  in  which  they  are  suspended  ;  and,  on  the  whole, 
it  seems  to  be  satisfactorily  settled  by  Mr.  Spence  Bate  (to 
whose  excellent  memoir  *  I  am  indebted  for  these  expla- 
natory details)  that  the  inner  antennae  are  real  ears. 

Having  thus  taken  our  Crab  by  the  ears,  we  will  en- 
deavour next  to  tweak  his  nose.  But  stay,  we  must  find 
it  first.  We  turn  our  horny  gentleman  up,  and  in  his  flat 
ancient  face  we  certainly  discern  little  sign  of  a  nasal 
organ.  Our  friend  Mr.  Bate  must  assist  us  again.  He 
will  tell  us  to  look  at  the  outer  or  lower  antennae.  We 
will  look,  accordingly,  magnifier  in  hand,  while  he  makes  it 
clear  to  us  that  these  are  a  pair  of  noses. 

Each  of  these  organs  is  formed  of  a  stem,  consisting  in 
general  of  five  joints  and  a  filament  of  many  minute  joints. 
In  the  Prawn  and  the  Lobster  all  the  five  joints  of  the  stem 
are  distinct ;  but  in  the  Crab  the  whole  are,  as  it  were, 
soldered  together  into  a  compact  mass,  so  that  the  sepa- 
rate articulations  are  scarcely  to  be  distinguished ;  while 
in  some  species  their  position  can  be  indicated  only  by  the 
presence  of  the  olfactory  operculum  or  lid. 

This  important  little  organ  varies  in  its  construction  in 
the  different  families  of  Crustacea.  In  the  Crab  it  is  a 
small  movable  appendage,  situated  at  the  point  of  junction 
between  the  second  and  third  joints ;  it  is  attached  to  a 
long  calcareous  lever-like  tendon,  at  the  extreme  limit  of 
which  is  placed  a  set  of  muscles,  by  which  it  is  opened 
and  closed  ;  to  assist  in  which  operation,  at  the  angle  of 
the  operculum  most  distant  from  the  central  line  of  the 
animal  are  fixed  two  small  hinges.  When  the  operculum 

*  "Annals  of  Nat.  Hist."  for  July,  1855. 


174  EVENINGS   AT    THE    MICROSCOPE. 

is  raised,  the  internal  surface  is  found  to  be  perforated  by 
a  circular  opening  protected  by  a  thin  membrane. 

In  the  Prawn,  Shrimp,  and  Lobster,  there  is  no  oper- 
culum,  but  only  the  orifice  covered  by  a  membrane,  which 
is  placed  at  the  extremity  of  a  small  protuberance,  and  is 
not  capable  of  being  withdrawn  into  the  cavity  of  the  an- 
tenna, as  in  the  Crab. 

In  the  latter  animal,  the  little  door,  when  it  is  raised, 
exposes  the  orifice  in  a  direction  pointing  to  the  mouth  ; 
and  where  there  is  no  door,  still  the  direction  of  the  open- 
ing is  the  same,  inwards  and  forwards,  answering  to  the 
position  of  the  nostrils  in  the  higher  animals.  In  each 
case  it  is  so  situated  that  it  is  impossible  for  any  food  to 
be  conveyed  into  the  mouth  without  passing  under  this 
organ  ;  and  there  most  conveniently  the  animal  is  enabled 
to  judge  of  the  suitability  of  any  substance  for  food,  by 
raising  the  little  door  and  applying  to  the  matter  to  be 
tested  the  sensitive  membrane  of  the  internal  orifice. 

Thus  it  is  concluded  that  this  lower  or  outer  pair  of  an- 
tennae are  the  proper  organs  of  smell,  as  the  upper  and 
inner  are  of  hearing.* 

The  eyes,  though  constructed  on  the  same  general  prin- 
ciples as  those  of  Insects,  yet  present  some  particulars 
worthy  of  your  notice.  In  the  Crabs  and  Lobsters  they 
consist  of  numerous  facets,  behind  each  of  which  is  a 
conical  or  prismatic  lens,  the  round  extremity  of  which  is 
fitted  into -a  transparent  conical  pit,  corresponding  to  a 
vitreous  body,  while  the  conical  extremity  of  these  lenses 
is  received  into  a  kind  of  cup,  formed  by  the  filaments  of 
the  optic  nerve.  Each  of  these  filaments,  together  with 
its  cup,  is  surrounded  by  pigment  matter,  in  a  sheath -like 
manner.  To  see  this  structure  would  require  anatomical 
skill ;  but  you  may  here  examine  with  a  low  power  por- 
tions of  the  cornea,  or  glassy  exterior,  of  the  eye  of 
a  Crab,  and  of  a  Lobster.  In  the  former,  you  see  that 

*  Op.  cit. 


CRABS    AND    SHRIMPS.  175 

the  facets  into  which  the  cornea  is  divided  are  hexagonal, 
like  those  of  most  Insects,  but  in  the  latter  they  are 
square. 

But  Crustacea  have  a  far  greater  faculty  of  circumspec- 
tion than  insects  have ;  for  besides  the  extensive  con- 
vexity and  numerous  facets  of  their  eyes,  these  organs  are 
placed  at  the  extremity  of  shelly  foot- stalks,  which  are 
themselves  movable  on  hinges,  capable  of  being  projected 
at  pleasure,  and  of  being  moved  in  different  directions, 
and  of  being  packed  snugly  away,  when  not  in  active  use, 
in  certain  grooves  hollowed  out  expressly  for  them  in  the 
front  margin  of  the  shell. 

We  might  find  much  more  both  instructive  and  amusing 
in  examining  microscopically  the  structure  of  the  higher 
Crustacea  ;  but  we  will  now  dismiss  them  in  order  to  dis- 
cuss some  of  the  lower  forms,  many  of  which  are  so 
minute  that  their  whole  bodies  may  be  watched  with  ease 
performing  all  the  functions  of  life,  while  confined  under 
our  eye,  on  the  stage  of  the  microscope.  I  refer  to  the 
tiny  active  little  creatures  known  as  Water-fleas,  which  are 
abundant  in  both  fresh  and  salt  water. 

In  this  jar  of  fresh  water,  which  has  been  standing  in 
the  window  for  weeks,  you  may  see  among  the  green  fila- 
ments of  Chara  many  little  atoms  which  scuttle  hither  and 
thither  with  a  rapid  succession  of  short  leaps.  These 
belong  to  the  genus  Cyclops,  and  are  Crustacea,  belonging 
to  the  order  ENTOMOSTRACA. 

By  the  aid  of  a  glass  tube  which  I  stop  at  one  end  with 
my  finger,  I  will  endeavour  to  catch  one.  It  is  no  easy 
matter,  as  you  see,  for  the  instant  the  end  of  the  tube  is 
brought  near  to  one,  he  takes  the  alarm  and  leaps  nimbly 
away  before  I  can  make  the  water  rush  in  by  withdraw- 
ing my  finger  from  the  other  end.  But  I  have  one  at 
length. 

Here  it  is  ;  a  living  atom,  not  more  than  a  sixteenth  of 
an  inch  in  length,  looking  something  like  a  pellucid  egg, 


176  EVENINGS    AT    THE   MICROSCOPE. 

furnished  with  long  antennae,  with  five  pairs  of  branching 
feet,  and  a  long  tail  terminating  in  bristles.  Bat  its  parts 
and  organs  must  not  be  dismissed  in  this  summary  way  ; 
we  must  look  at  them  in  detail. 

And,  first  of  all,  in  the  very  midst  of  its  forehead,  like 
that  obscene  giant  *  after  whom  our  tiny  friend  is  named, 
—•it  possesses  a  single  eye  that  glares  like  a  ruby.  It 
would  need  no  vast  beam  of  olive-wood,  sharpened  and 
heated  in  the  fire,  and  "twirled  about"  by  the  united 
strength  of  five  heroes,  to  "grind  the  pupil  out;"  for 
though  brilliant  and  mobile,  it  is  far  too  minute  to  be 
touched  by  the  tip  of  the  finest  needle.  Yet  it  is  elabo- 
rately constructed ;  for  it  consists  of  a  number  (not  very 
large)  of  simple  eyes  placed  beneath  a  common  glassy 
cornea.  Several  muscle -bands  are  attached  to  this  com- 
pound organ  of  vision,  and  are  arranged  so  as  to  form  a 
cone,  of  which  the  eye  is  the  base ;  these  give  the  eye 
a  movement  of  rotation  upon  its  centre,  which  may  be  dis- 
tinctly seen. 

All  the  limbs,  including  both  pairs  of  antennas,  two 
pairs  of  foot-jaws,  five  pairs  of  feet,  and  a  pair  of  tail- 
lobes,  are  furnished  at  each  of  their  many  joints  with  tufts 
of  long  hairs  ;  these  appear  to  act  the  part  of  paddles,  as 
the  active  little  animal  strikes  the  water  vigorously  with 
all  its  limbs,  for  the  purpose  of  progression,  and  also  for 
the  creation  of  currents  in  the  fluid,  which  currents  sub- 
serve a  double  object, — the  bringing  constant  supplies 
of  water  to  be  respired  and  floating  atoms  of  food  to  be 
devoured. 

In  this  individual,  which  is  a  female,  the  antennae  are, 
nearly  equal  in  size  throughout  their  length  ;  but,  in  the 
male,  the  middle  joints  of  the  upper  pair  are  remarkably 
enlarged,  forming  a  large  swelling,  followed  by  a  sudden 
contraction,  the  first  part  of  which  is  hinged.  All  of  the 
true  feet  and  the  second  pair  of  foot-jaws  are  divided  to 
the  base  into  two  equal  branches,  so  that  the  animal 

3.  IX. 


CRABS   AND   SHRIMPS.  177 

seems  to  possess  no  fewer  than  twenty-six  limbs  :  each 
of  which  being  many -jointed,  and  each  joint,  as  I  have 
observed,  being  set  with  delicately-plumose  hairs,  the 
whole  effect  is  most  elegantly  light  and  feathery. 

On  each  side  of  the  slender  tail-like  abdomen  you  see 
an  oval  bag,  connected  with  the  body  by  an  exceedingly 
slender  thread  of  communication,  and  tightly  filled  with 
pellucid  globose  bodies.  Like  John  Gilpin,  of  equestrian 
fame,  when 


:  He  hung  a  bottle  on  each  side 
To  keep  his  balance  true," 


our  little  natatory  harlequin  "  carries  weight."  But  these 
bags  are  filled  with  eggs,  a  temporary  provision  for  their 
due  and  proper  exposure  to  the  water,  while  yet  they  are 
protected  from  enemies.  They  are  developed  only  at 
certain  seasons,  when  the  eggs,  having  attained  a  given 
amount  of  maturity  in  the  ovary,  are  transferred  through 
the  exceedingly  slender  tube  into  these  sacs,  and  are  there 
carried  about  by  the  mother  until  the  young  are  hatched, 
when  the  curious  receptacles,  being  no  longer  needed,  are 
thrown  off  and  speedily  decay. 

Here  is  a  second  form.  It  is  named  Lynceus,  and  is 
nearly  as  common  as  the  Cyclops  in  our  stagnant  pools. 
Essentially  its  structure  is  the  same  ;  but  it  has  this  pecu- 
liarity, that  its  body  is  inclosed  within  a  transparent  shell, 
which  is  thin  and  flattened  sidewise,  and  through  whose 
walls  all  the  movements  and  functions  of  its  parts  are  dis- 
tinctly visible.  The  shell  is  broadly  ovate  in  outline, 
comes  to  a  sharp  edge  all  along  one  half  of  its  circum- 
ference, but  is  open  all  along  the  other  ;  as  if  two  watch- 
glasses  were  soldered  together,  edge  to  edge,  and  then  a 
portion  of  the  edges  ground  away,  so  as  to  leave  a  narrow 
but  long  entrance.  Through  this  narrow  orifice  the  limbs 
are  protruded  for  locomotion ;  and  through  it  the  surround - 

N 


178  EVENINGS    AT    THE    MICROSCOPE. 

ing  water  finds  its  way  in  currents,  bringing  oxygen  to  be 
respired  and  food  to  be  devoured. 

The  translucent  shell  descends  in  front  into  a  sharp 
long  beak,  below  which  are  seen  the  organs  of  the  mouth, 
two  pairs  of  foot-jaws,  beset  with  fine  bristles.  At  the 
origin  of  the  beak  is  the  eye,  consisting,  as  we  saw  in  the 
Cyclops,  of  several  lenses,  enveloped  in  a  common  cornea, 
the  whole  forming  a  movable  organ  of  a  blue-black  hue. 
Just  behind  this,  at  the  very  highest  part  of  the  shell, 
is  a  little  colourless  bladder-like  vesicle,  which  constantly 
maintains  a  rapidly  alternate  contraction  and  dilatation. 
This  is  the  heart,  and  this  motion  circulates  the  blood. 

Below  this,  there  is  seen  a  great  translucent  irregular 
mass  of  flesh,  evidently  comprising  many  viscera,  which 
winds  along  from  one  end  of  the  shell  to  the  other,  nearly 
occupying  its  entire  area.  It  is  not  in  connexion  with  it  at 
the  hinder  part,  as  we  see  by  its  free  movements  there, 
where  it  curves  round,  and,  bending  beneath,  terminates  in 
a  blunt  tail,  armed  with  two  strong  hooks,  which  can  at 
pleasure  be  thrust  down  through  the  narrow  orifice  of  the 
shell  and  become  partially  straightened  by  being  forcibly 
thrown  backward.  This  great  central  mass  is  mainly 
occupied  by  the  alimentary  canal,  in  which  food  in  various 
stages  of  assimilation  may  at  all  times  be  seen,  and  in 
which  the  interesting  function  of  digestion  can  be  wit- 
nessed throughout,  from  the  first  seizure  of  the  atom  and 
its  mastication  by  the  jaws,  to  the  discharge  of  the  useless 
remains. 

The  individual  before  us  does  not  carry  at  this  time 
eggs  in  the  process  of  development ;  but  the  deficiency  is 
supplied  by  a  Daphnia  which  is  playing  about  in  the  same 
drop  of  water.  Here  you  perceive,  between  the  arched 
outline  of  the  shell  and  the  sinuous  outline  of  the  free 
soft  body,  an  open  space  of  some  size,  which  constitutes  a 
receptacle,  in  which  the  eggs  are  deposited  as  they  are 
laid,  and  in  which  they  remain  not  only  until  the  little 


GRABS   AND    SHEIMPS.  179 

animals  are  hatched,  but  until  they  have  acquired  a  suffi- 
cient maturity  to  swim  about  and  get  their  independent 
living. 

This  receptacle,  in  which  you  may  see  five  or  six  eggs, 
is  freely  open  to  the  surrounding  water,  which  enters 
the  slit  edge  of  the  shell  behind  the  tail.  Perhaps  you 
wonder  why  the  eggs  are  not  washed  out  by  the  respiratory 
currents  ;  they  are,  in  fact,  maintained  in  their  position 
only  by  a  slender  tongue-like  projection  from  the  back  of  the 
parent,  which  appears  to  have  that  special  object.  When, 
however,  the  young  are  ready  for  freedom,  the  mother  has 


but  to  depress  her  body  a  little  more  than  ordinary,  when 
the  door  is  opened  and  the  young  easily  slip  from  the  re- 
ceptacle into  the  open  water. 

These  tiny  odd-looking  sprawling  things  that  you  see 
moving  about  by  quick  jerks  in  the  same  drop  of  water, 
are  the  young  recently  hatched.  They  are  quite  unlike 
their  parent,  having  as  yet  no  bivalve  shell,  no  abdomen, 
and  only  three  pairs  of  limbs.  The  body  is  a  transparent 
plate,  resembling  the  bowl  of  a  spoon  in  form,  but  ending 
in  two  points  which  carry  pencils  of  bristles.  The  large 

N2 


180  EVENINGS    AT    THE    MICROSCOPE. 

dark  eye  is  conspicuous  in  front,  and  the  six-jointed  and 
bristled  limbs  radiate  from  the  centre,  projecting  stiffly  on 
all  sides.  The  second  and  third  pairs  are  seen  to  be 
double,  each  giving  off  a  branch,  which  is  pencilled  with 
bristles  like  the  principal  stem. 

We  have  not  yet  done  with  these  tiny  Water-fleas.  The 
sediment  at  the  bottom  of  this  jar  of  water  is  quite  alive 
with  a  host  of  nimble  atoms,  some  of  which  you  may  see 
crawling  up  the  sides  of  the  glass.  They  are  quite  distinct 
from  either  of  the  kinds  we  have  been  examining,  not  only 
in  details  of  structure,  which  is  more  identical,  indeed, 
than  it  seems  at  first  sight,  but  in  habit ;  for  whereas  they 
shoot  to  and  fro  through  the  water  with  great  force  and 
rapidity,  these  can  scarcely  swim  at  all ;  or,  if  they  do,  it 
is  with  comparative  slowness  and  much  apparent  effort ; 
though  over  the  smooth  side  of  their  glass  dwelling,  or 
upon  the  stems  of  water-plants,  they  glide  along  with  much 
ease  and  elegance  by  the  quick  vibrations  of  their  pen- 
cilled feet. 

The  form  we  are  now  contemplating  is  distinguished  by 
the  name  of  Cypris,  a  genus  which  contains  a  good  many 
British  species.  It  is  more  completely  inclosed  in  a  shell 
than  even  the  Lynceus,  and  its  envelope  more  truly  re- 
sembles the  shell  of  a  bivalve  Mollusk,  for  the  valves  are 
open  for  more  than  three-fourths  of  their  circumference ; 
while  the  portion  of  the  back  that  is  united  is  sufficiently 
elastic  to  allow  of  some  degree  of  expansion,  thus  answer- 
ing the  purpose  of  a  hinge. 

Now  look  at  the  elegant  little  creature.  Its  most  pro- 
minent feature  is  its  two  pairs  of  antennae,  one  projecting 
forwards  and  curved  upwards,  the  other  downwards.  Both 
consist  of  several  transparent  joints,  and  are  tipped  with 
long  clear  bristles;  but  the  pencils  which  tip  the  upper 
pair  are  specially  graceful,  being  as  long  as  the  whole 
shell,  exceedingly  slender,  beautifully  curved,  and  so  trans- 
parent that  they  seem  formed  of  spun  glass. 


CBABS   AND    SHRIMPS.  181 

Another  peculiarity  is,  that  there  seems  to  be  but  one 
pair  of  legs,  which  terminate  each  in  a  hooked  spine. 
You  now  and  then  see  these  awkwardly  thrust  out  from 
beneath  the  hinder  part  of  the  shell,  but  locomotion  is 
principally  effected  by  the  pencilled  antennae.  There  is, 
however,  a  second  pair  of  legs,  but  these  do  not  usually 
make  their  appearance  outside  the  shell,  being  curved 
backwards  to  sustain  the  ovaries. 


About  forty-five  years  ago  an  Irish  naturalist,  Dr.  J. 
Vaughan  Thompson,  announced  a  discovery,  which,  up- 
setting conclusions  previously  received  by  all,  caused  no 
little  dissent  and  opposition,  and  gave  rise  to  a  lengthened 
and  wide-spread  controversy.  A  very  minute  crustaceous 
animal  was  known,  as  inhabiting  the  open  sea,  to  which 
the  name  of  Zoea  had  been  given.  It  had  sessile  (i.e.,  not 
stalked)  eyes,  and  was  remarkable  for  having  a  long  spine 
projecting  from  the  face,  and  a  similar  one  standing  up 
from  the  centre  of  the  back.  Another  form  was  known, 
which  constituted  the  genus  Megalopa ;  in  which  the  body 
was  broad,  the  eyes  stalked,  and  the  abdomen  projecting 
behind.  This  was  also  small,  but  somewhat  larger  than 
the  preceding. 

Nobody  suspected   that  these   were  other  than  inde- 


182  EVENINGS   AT    THE    MICROSCOPE. 

pendent  forms  of  animal  life,  distinct  from  each  other, 
and  equally  distinct  from  every  known  genus  of  Crustacea 
besides.  It  was  supposed  that  no  animal  of  this  class 
underwent  metamorphosis,  or  that  change  of  form  in 
different  periods  of  life  which  distinguishes  Insects ;  but 
that  these  creatures  retained  through  life  the  general  shape, 
slightly  modified  by  development  of  parts  and  organs, 
which  they  each  displayed  when  hatched  from  the  egg. 

But  these  conclusions  were  quite  set  aside  by  the  bril- 
liant discovery  of  Thompson,  that  Zoea  and  Megalopa 
were  the  same  animal  in  different  stages  of  existence ;  and 
that,  moreover,  both  were  but  the  early  states  of  well- 
known  and  familiar  forms  of  larger  Crustacea,  which  there- 
fore undergo  a  metamorphosis  as  complete  as  that  by 
which  the  caterpillar  changes  to  a  chrysalis,  and  the  chry- 
salis to  a  butterfly,  and  in  every  essential  point  parallel  to  it. 

In  the  Cove  of  Cork  this  naturalist  met  with  a  con- 
siderable number  of  Zoeas,  which  he  kept  in  captivity. 
Some  of  these  passed  into  the  Megalopa  form,  which  in 
turn  changed  to  the  most  abundant  of  all  our  larger  Crus- 
tacea, the  common  Shore-crab  (Carcinus  nuenas).  "  Thus, 
in  its  progress  from  the  egg  to  its  final  development,  the 
Crab  was  proved  to  pass  through  two  temporary  condi- 
tions, which  had  previously  been  regarded  as  types,  not  of 
general  only,  but  of  different  families ;  and  both  strikingly 
dissimilar  from  the  group  to  which,  in  its  perfect  state,  it 
belongs/' 

I  have  not  myself  examined  the  transformations  of  this 
species ;  but,  as  they  have  been  well  worked  out,  and  as 
the  animal  is  so  abundant  everywhere  on  the  coast  that 
you  may  easily  verify  what  has  been  observed,  I  will  cite 
you  the  elaborate  account  of  Mr.  R.  Q.  Couch,  of  Pen- 
zance,  who  has  investigated  the  subject  with  great  skill, 
zeal,  and  success. 

Having  procured  some  specimens  of  the  Shore-crab 
laden  with  eggs  just  ready  for  shedding,  he  goes  on  to  say, 


CRABS    AND    SHRIMPS.  183 

"  These  were  transferred  to  captivity,  placed  in  separate 
basins,  and  supplied  with  sea-water ;  and  in  about  sixteen 
hours  I  had  the  gratification  of  finding  large  numbers  of 
the  creatures  alluded  to  above,  swimming  about  with  all 
the  activity  of  young  life.  There  could  be  but  little  doubt 
that  these  creatures  were  the  young  of  the  captive  Crabs.  In 
order,  however,  to  secure  accuracy  of  result,  one  of  the  Crabs 


ZOEA   OF   SHORE-CRAB. 


was  removed  to  another  vessel,  and  supplied  with  filtered 
water,  that  all  insects  might  be  removed ;  but  in  about  an 
hour,  the  same  creatures  were  observed  swimming  about 
as  before.  To  render  the  matter,  if  possible,  still  more 
certain,  some  of  the  ova  were  opened  and  the  embryos 
extracted ;  but  shortly  afterwards  I  had  the  pleasure  of  wit- 
nessing, beneath  the  microscope,  the  natural  bursting  and 
escape  of  one  precisely  similar  in  form  to  those  found  so 
abundantly  in  the  water.  Thus,  then,  there  is  no  doubt 
that  these  grotesque-looking  creatures  are  the  young  of 
the  Carcinus  m<znas ;  but  how  different  they  are  from  the 


184  EVENINGS    AT    THE    MICEOSCOPE. 

adult  need  hardly  be  pointed  out  any  further  than  by  re- 
ferring to  the  figure.  When  they  first  escape  they  rarely 
exceed  half  a  line  in  length.  The  body  is  ovoid,  the 
dorsal  shield  large  and  inflated;  on  its  upper  edge  and 
about  the  middle  is  a  long  spine,  curved  posteriorly,  and 
rather  longer  than  the  diameter  of  the  body,  though  it 
varies  in  length  in  different  specimens  ;  it  is  hollow,  and 
the  blood  may  be  seen  circulating  through  it.  The  upper 
portion  of  the  body  is  sap-green,  and  the  lower  semi- 
transparent.  The  eyes  are  large,  sessile,  and  situated  in 
front,  and  the  circumference  of  the  pupil  is  marked  with 
radiating  lines.  The  lower  margin  of  the  shield  is  waved, 
and  at  its  posterior  and  lateral  margin  is  a  pair  of  nata- 
tory feet.  The  tail  is  extended,  longer  than  the  diameter 
of  the  shield ;  and  is  composed  of  five  equal  annulations, 
besides  the  terminal  one  ;  its  extremity  is  forked,  and  the 
external  angles  are  long,  slender,  pointed,  and  attached  to 
the  last  annulation  by  joints.  Between  the  external  angles 
and  on  each  side  of  the  median  line  are  three  lesser  spines, 
also  attached  to  the  last  ring  by  joints.  Between  the  eyes, 
and  from  near  the  edge  of  the  shield,  hangs  a  long,  stout, 
and  somewhat  compressed  appendage,  which,  as  the 
animal  moves,  is  reflexed  posteriorly  between  the  claws. 
Under  each  eye  is  another  appendage,  shorter  and  slightly 
more  compressed.  The  claws  are  in  three  pairs  ;  each  is 
composed  of  three  joints,  and  terminates  in  four  long, 
slender,  hair-like  appendages.  These  claws  are  generally 
bent  on  the  body,  but  stand  in  relief  from  it.  If  the 
animal  be  viewed  in  front,  the  lower  margin  of  the  dorsal 
shield  will  be  found  to  be  waved  into  three  semi-circular 
festoons,  the  two  external  of  which  are  occupied  by  the 
eyes,  and  between  which  the  middle  one  intervenes ;  the 
general  direction  of  the  claws  will  be  seen  to  be  at  right 
angles  to  the  body.  As  the  young  lies  inclosed  within  the 
membranes  of  the  egg,  the  claws  are  folded  on  each  other, 
and  the  tail  is  flexed  on  them  so  far  as  the  margin  of  the 


CRABS    AND    SHRIMPS.  185 

shield,  and,  if  long  enough,  is  reflected  over  the  front  of 
the  shield  between  the  eyes.  The  dorsal  spine  is  bent 
backwards  and  lies  in  contact  with  the  dorsal  shield ;  for 
the  young,  when  it  escapes  from  the  egg,  is  quite  soft,  but 
it  rapidly  hardens  and  solidifies  by  the  deposition  of  cal- 
careous matter  in  what  may  be  called  its  skin.  The  pro- 
gress of  this  solidification  may  be  very  beautifully  observed 


SECOND   STAGE   OF   SHORE-CRAB. 

(Megalopa.) 


by  watching  the  circulation  in  the  dorsal  spine.  When 
the  creature  has  just  effected  its  liberation  from  the  egg, 
the  blood-globules  may  be  seen  ascending  to  the  apex ; 
but  as  the  consolidation  advances,  the  circulation  becomes 
more  and  more  limited  in  its  extent,  and  is  finally  con- 
fined to  the  base.  These  minute  creatures,  in  this  early 
state  of  their  existence,  are  natatory  and  wonderfully 
active.  They  are  continually  swimming  from  one  part  of 
the  vessel  to  the  other  ;  and,  when  observed  free  in  their 


186  EVENINGS    AT    THE    MICKOSCOPE. 

native  pools,  are,  if  possible,  even  more  active  than  when 
in  confinement.  Their  swimming  is  produced  by  con- 
tinued flexions  and  extensions  of  the  tail,  and  by  repeated 
beating  motions  of  their  claws  ;  this,  together  with  their 
grotesque-looking  forms,  gives  them  a  most  extraordinary 
appearance  when  under  examination.  As  the  shell  be- 
comes more  solid  they  get  less  active,  and  retire  to  the 
sand  at  the  bottom  of  the  vessel,  to  cast  their  shells  and 
acquire  a  new  form.  They  are  exceedingly  delicate,  and 
require  great  care  and  attention  to  carry  them  through  the 
first  stage ;  for  unless  the  water  be  supplied  very  fre- 
quently and  in  great  abundance,  they  soon  die. 

"  The  second  form  of  transmutation  is  equally  as  re- 
markable as  the  first,  and  quite  as  distinct  from  the  adult 
animal.  In  the  species  now  under  consideration  this 
second  transformation  is  marked  by  the  disappearance  of 
the  dorsal  spine  ;  the  shield  becomes  flatter  and  more 
depressed,  the  anterior  portion  more  horizontal  and 
pointed,  the  three  festoons  having  disappeared.  The 
eyes,  from  being  sessile,  are  now  elevated  on  foot-stalks, 
the  infra-orbital  appendages  become  apparently  converted 
into  antennsB.  The  claws  undergo  an  entire  revolution  ; 
the  first  pair  become  stouter  than  the  others,  and  are 
armed  with  a  pair  of  nippers,"  the  others  being  simple ; 
"  but  the  posterior  pair  are  branched  near  the  base,  and 
one  of  the  branches  ends  in  a  bushy  tuft.  The  tail  is 
greatly  diminished  in  its  relative  size  and  proportions,  and 
is  sometimes  partially  bent  under  the  body,  but  is  more 
commonly  extended.  This  form  is  as  natatory  as  the 
first.  They  are  frequently  found  congregating  around 
floating  sea-weed,  the  buoys  and  strings  of  the  crab-pot 
marks,  and  other  floating  substances,  both  near  the  shore 
and  in  deep  water.  Their  general  form  somewhat  re- 
sembles a  Galathea."'* 

*  "  Rep.  Cornw.  Polyt.  Soc.,"  1843. 


CRABS   AND    SHRIMPS.  187 

Thus,  under  Mr.  Couch's  eye,  the  Zoea  had  changed  to 
a  Megalopa ;  and  this  latter  became  after  a  short  time  a 
Crab,  in  which  were  all  the  characters  that  belong  to  the 
order  to  which  the  parent  belongs ;  but  not  those  of  the 
genus  nor  even  of  the  family.  Its  form  bore  a  close 
resemblance  to  that  of  the  Sargasso  Crabs  (Grapsida) ; 
for  the  shield,  instead  of  being  large  and  arched  in  front, 
and  narrowed  behind,  was  nearly  square,  while  the  front 
was  (taking  in  the  eyes)  almost  straight,  the  lateral  angles 
much  advanced. 


THIRD   STAGE    OF    SHORE-CRAB. 

(Grapsoid.) 


This  Crab,  however,  was  still  very  minute ;  and  many 
sloughings  were  before  it.  In  the  course  of  these  it  was 
destined  gradually  to  attain  not  only  the  dimensions  of  its 
parents,  but  also  their  form.  This,  however,  would  be 
matter  of  development  rather  than  metamorphosis :  the 
lateral  outlines  of  the  shield  would  more  and  more  ap- 
proach each  other  behind,  while  the  series  of  points  that 
now  belonged  to  these  lateral  outlines  would  become  thrown 
into  the  front  margin,  which  would  by  degrees  assume  an 
arched  form,  as  you  may  see  in  the  figure  of  the  adult  Crab. 

Though  I  cannot  at  this  moment  show  you  specimens  of 
the  Carcinus  in  its  earlier  stages,  yet  I  have  here  a  good 
number  of  the  Zoeas  of  one  of  those  intermediate  forms 
which  are  the  connecting  links  between  the  Crabs  and 


188 


EVENINGS    AT    THE    MICROSCOPE. 


Lobsters :  I  mean  Galathea.  The  adult  animal  is  of  a 
broad  squat  form,  something  like  what  you  might  suppose 
a  Lobster  to  be,  if  it  had  been  flattened  between  two 
stones,  without  being  actually  destroyed.  We  have  two 
or  three  species,  one  of  which  is  adorned  with  brilliant 
scarlet  and  azure  paintings ;  but  I  cannot  tell  to  which  of 
them  all  this  infant  form  belongs. 


ADULT    SHORE-CRAB. 


You  perceive  that  there  is  a  general  similarity  between 
these  transparent  little  creatures  and  the  Zoea  described  by 
Mr.  Couch ;  but  there  are  great  differences  in  detail. 
The  glassy  shield  or  carapace  shoots  out  in  front  in  a  stiff, 
inflexible,  very  fragile  spine.  This  is  perfectly  straight, 
and  nearly  thrice  the  length  of  the  whole  shield.  It  is 
beset,  on  various  lines  on  its  surface,  with  short  slender 
spinules  jointed  to  shoulder-like  angles,  and  not  serratures. 
Its  interior  is  perforated  by  a  canal  which  dilates  and  nar- 
rows irregularly.  The  carapace  posteriorly  is  semi-oval, 
projecting  a  transparent  convex  vault  over  the  part  where 


CBABS  AND  SHRIMPS.  189 

the  abdomen  is  attached  to  it,  as  is  seen  when  the  latter 
bends  down.  Its  extremity  gradually  tapers  into  two 
straight,  sub-parallel,  stiff  spines,  about  as  long  as  the 
carapace  itself,  each  terminating  in  a  hooked  point. 

The  abdomen  ends  in  a  spinous  plate,  which  is  very 
elegantly  lozenge- shaped  and  beset  with  spines.  Each  of 
the  two  latero-posterior  edges  of  the  lozenge  is  cut  into 
six  rectangular  teeth,  and  each  tooth  bears  on  its  hinder 
face  a  long  spine,  articulated  to  it,  and  most  delicately 
plumose  all  along  its  sides.  The  hindermost  pair  of  spines 
are  short,  and  are  set  close  together,  side  by  side.  Be- 
sides these  jointed  spines,  each  lateral  angle  of  the  lozenge- 
shaped  tail-plate  projects  into  a  spine-like  tooth. 

Though  the  individuals  before  us  are  all  in  the  same 
state  as  to  the  stage  of  their  development,  there  is  some 
difference  in  size,  indicating,  doubtless,  a  corresponding 
diversity  in  age.  We  will  isolate  a  few  of  the  largest  and 
put  them  into  a  glass  trough  for  microscopical  examination. 

The  largest,  during  the  few  minutes  which  I  have 
occupied  in  the  process  of  dipping  them  out,  has  undergone 
a  metamorphosis.  You  observed  that,  after  skipping  about 
the  trough  for  a  few  minutes,  it  sank  quietly  to  the  bottom, 
where  it  lay  on  its  back  ;  the  next  thing  that  you  see  is  a 
much  more  crab-like  animal,  more  opaque,  redder,  much 
larger,  but  lying  on  its  back  in  the  very  spot  where  a 
moment  before  you  had  seen  a  Zoea ;  while  close  by  it 
lies  the  transparent  filmy  skin  which  has  been  cast  off. 

The  new  animal  is  evidently  now  in  its  final  state, 
needing  only  development  of  its  parts,  which  it  would 
obtain,  if  in  freedom,  by  successive  moults,  to  acquire  the 
adult  form. 

If  we  now  submit  the  exuviae  in  detail  to  a  power  of  220 
diameters,  we  shall  obtain  some  interesting  views  of  the 
structure.  The  slough  of  the  eyes  in  particular  presents 
one  of  the  most  exquisite  objects  that  you  can  behold. 
They  are  somewhat  pear-shaped,  with  the  facetted  portion 


190  EVENINGS    AT    THE    MICROSCOPE. 

well  defined.  It  is  the  appearance  of  these  facets,  varying 
according  as  the  perfectly  hexagonal  outline  of  each,  or 
the  smooth  and  glossy  convexity,  comes  into  focus,  that 
is  so  peculiarly  charming. 

Returning  now  to  the  examination  of  one  of  the  living 
Zoeas,  you  perceive  that  the  three  pairs  of  pencilled  limhs 
do  not  represent  any  of  the  true  legs;  for  the  trans- 
parency of  the  integuments  allowing  the  interior  to  be 
clearly  seen,  and  the  organs  of  the  imago  being  matured 
and  just  ready  for  sloughing,  you  discern,  with  the  most 
beautiful  distinctness,  the  fingered  claws  (short  and  stumpy, 
it  is  true,  as  compared  with  their  perfect  form  in  the 
newly-freed  imago)  folded  down  upon  the  breast  within  the 
skin,  the  second  pair  as  large  as  these,  and  traces  of 
others  beneath  them, — all  these  forming  two  great  pro- 
jecting lobes,  slightly  movable,  beneath  the  thorax  of  the 
Zoea,  and  occupying  a  bulk  nearly  equal  to  that  of  the 
whole  shield. 

The  circulation  of  the  blood  is  beautifully  clear.  The 
pellucid  colourless  globules  chase  each  other  by  starts  to 
and  fro,  as  the  eye  rests  on  the  outgoing  or  returning 
current.  It  is  distinct  in  some  parts  where  you  would 
scarcely  have  looked  for  it ;  as  all  over  the  lozenge  plate 
of  the  tail,  in  the  interior  of  the  eyes,  throughout  the 
posterior  spines  of  the  shield,  and  the  frontal  spine.  But 
besides,  and  apparently  independent  of,  the  circulation, 
there  is  a  singular  fusiform  vessel  in  the  latter  segments  of 
the  abdomen,  penetrating  the  tail-plate,  on  the  ventral 
side.  This  vessel,  now  and  then,  at  irregular  intervals, 
dilates  quickly  and  closes  ;  the  wave  proceeding  upward 
toward  the  head,  but  only  for  a  short  distance,  and  un- 
attended with  any  impulse  to  the  blood-globules.  The 
nature  of  this  vessel,  and  its  use  in  the  economy  of  the 
infant  Crab,  I  can  in  no  wise  explain.* 

*  For  figures  of  these  two  forms  the  reader  is  referred  to  my  Tenby, 
170, 172. 


BARNACLES.  191 


CHAPTER  XII. 

BABNACLES. 

You  cannot  have  wandered  among  the  rocks  on  our 
southern  or  western  coasts,  when  the  tide  is  out,  without 
having  observed  that  their  whole  surface,  up  to  a  certain 
level  (often  very  precisely  denned),  is  roughened  with  an 
innumerable  multitude  of  little  brownish  cones.  If  you 
have  ever  thought  it  worth  while  to  examine  them  with 
more  care,  you  have  seen  that,  crowded  as  they  are,  so 
thickly  that  frequently  they  crush  each  other  out  of  their 
proper  form  and  proportions,  they  are  all  constructed  on 
the  same  model.  Each  cone  is  seen  to  be  a  little  castle, 
built  up  of  stony  plates  that  lean  towards  each  other,  but 
which  leave  an  orifice  at  the  top.  Within  this  opening, 
provided  the  castle  be  tenanted  by  a  living  inhabitant,  you 
see  two  or  three  other  pieces  joined  together  in  a  peculiar 
manner,  which  are  capable  of  separating,  but  which,  when 
brought  together,  effectually  close  up  all  ingress. 

Perhaps  you  have  never  pushed  your  investigations 
farther  than  this,  having  a  courteous  respect  for  the  feel- 
ings of  the  inmate,  which  has  prevented  your  intruding  on 
a  privacy  so  secluded.  But  I  have  been  less  considerate ; 
many  a  time  have  I  applied  the  steel  chisel  and  hammer 
to  the  solid  rock,  and  having  cut  off  some  projecting  piece 
or  angle,  have  transferred  it,  all  covered  with  its  stony 
cones,  to  the  interior  of  a  glass  tank  of  sea- water,  for 
more  intimate  acquaintance  with  the  little  builders  at  my 
leisure. 


192  EVENINGS    AT    THE    MICROSCOPE. 

These  are  Barnacles  (Balanidce).  Such  a  colony  I  have 
now  in  my  possession,  which  I  will  submit  to  you,  for  they 
present  a  beautiful  and  highly  interesting  spectacle,  when 
engaged  in  their  ordinary  employment  of  fishing  for  a  sub- 
sistence. And  not  only  so,  but  I  have  living  specimens  of 
a  much  larger  and  finer  species  than  the  common  one, — 
the  Belanus  porcatus,  whose  castle  stands  an  inch  or  more 
in  height.  The  structure,  however,  and  habits  are  pretty 
much  the  same  in  both. 

Without  disturbing  the  busy  fishers,  then,  just  take 
your  seat  in  front  of  this  tank,  and,  with  a  lens  before 
your  eye,  watch  the  colony  which  is  seated  on  that  piece 
of  stone,  close  to  the  glass  side.  From  one  and  another, 
every  instant,  a  delicate  hand  is  thrust  forth,  and  presently 
withdrawn.  Fix  your  attention  on  some  one  conveniently 
placed  for  observation.  It  is  now  closed;  but  in  a 
moment,  a  slit  opens  in  the  valves  within  the  general 
orifice,  displaying  a  black  lining  with  pale  blue  edges ;  it 
widens  to  an  oval ;  the  pointed  valves  are  projected,  and 
an  apparatus  of  delicate  curled  filaments  is  thrust  quickly 
out,  expanding  and  uncurling  as  it  comes,  to  the  form  of  a 
fan  ;  then  in  an  instant  more  the  tips  of  all  the  threads 
again  curl  up,  the  threads  collapse,  and  the  whole  appa- 
ratus is  quickly  withdrawn,  and  disappears  beneath  the 
closing  valves.  The  next  moment,  however,  they  re-open, 
and^the  little  hand  of  delicate  fingers  makes  another  grasp, 
and  so  the  process  is  continually  repeated  while  this 
season  of  activity  endures. 

Now,  by  putting  this  specimen  into  a  glass  trough,  and 
placing  it  under  a  low  power  of  the  microscope,  we  shall 
see  what  an  exquisite  piece  of  mechanism  it  is.  The  little 
hand  consists  of  twenty-four  long  fingers,  of  the  most 
delicate  tenuity,  each  composed  of  a  great  number  of 
joints,  and  much  resembling  in  this  respect  the  antennae  of 
a  Beetle.  These  fingers  surround  the  mouth,  which  is 
placed  at  the  bottom  of  the  sort  of  imperfect  funnel  formed 


EABNACLES. 


193 


by  their  divergence.  They  resolve  themselves  into  six 
pairs  of  arms ;  for  each  one  is  branched  from  the  basal 
joint,  dividing  into  two  equal  and  similar  portions.  Those 
nearest  the  mouth  are  the  shortest ;  and  each  pair  increases 
regularly  in  length  to  the  most  distant,  which  are  the 
central  pair  when  the  hand  is  extended.  Each  division  of 
each  of  this  longest  and  most  extensile  pair  comprises,  in 
the  specimen  before  us,  thirty-two  joints,  while  the  shortest 
consists  of  about  ten,  the  intermediate  ones  being  in  pro- 
portion ;  so  that  the  whole  apparatus  includes  nearly  five 
hundred  distinct  articulations  ;  a  wonderful  provision  for 
flexibility,  seeing  that  every  joint  is  worked  by  its  own 
proper  system  of  muscles. 

Moreover,  every  separate  joint  is  furnished  with  its  own 
system  of  spinous  hairs,  which  are  doubtless  delicate 
organs  of  touch,  since  it  has  been  established  that  the 
hairs  with  which  the  shelly  coats  of  Crustacea  are  studded, 
pass  through  the  substance  of  the  latter,  and  communicate 
with  a  pulpy  mass,  richly  sup- 
plied with  nerves,  which  lines 
the  shell. *  These  hairs  project 
at  a  more  or  less  wide  angle 
from  the  axis  of  the  finger-like 
filament,  and  are  graduated  in 
length ;  and,  what  is  very  striking, 
as  illustrating  the  exquisite  work- 
manship of  the  Divine  hand,  the 
hairs  themselves  are  compound 
structures;  for  under  a  high 
power  they  seem  to  be  composed 
of  numerous  joints, — a  deceptive 
appearance,  probably,  what  look 
like  joints  being  rather  successive 
shoulders,  or  projections  and  con- 
strictions of  the  outline, — while 

*  "  Proc.  Royal  Society,"  ix.  215. 
o 


HAND   OF   BARNACLE. 


194  EVENINGS   AT    THE    MICROSCOPE. 

each  shoulder  carries  a  whorl  of  finer  spines,  lying  nearly 
close  to  the  main  hair,  and  scarcely  deviating  from  its 
general  direction.  This  barbed  structure  of  the  hairs  is 
chiefly  seen  towards  their  attenuated  extremities. 

And  now  do  you  ask, — What  is  the  object  of  this 
elaborate  contrivance,  or  rather  series  of  contrivances  ? 
I  answer, — It  is  the  net  with  which  the  fisher  takes  his 
food :  it  is  his  means  of  living.  You  have  seen  that  the 
animal  has  no  power  of  pursuing  prey :  he  is  immovably 
fixed  to  the  walls  of  his  castle,  which  is  immovably 
fixed  to  the  solid  rock.  He  is  compelled  therefore  to 
subsist  on  what  passes  his  castle,  and  on  what  he  can 
catch  as  he  sits  in  his  doorway,  and  casts  his  net  at 
random. 

You  saw,  also,  with  what  a  regular  perseverance  the 
casts  were  made ;  and  now  that  you  have  examined  in 
detail  the  construction  of  the  net,  you  are  prepared  to  ap- 
preciate its  fitness  for  the  work  assigned  to  it.  Its  extreme 
flexibility,  produced  by  the  number  of  its  joints,  enables 
the  fingers  of  the  hand,  or  the  threads  of  the  net  (which 
you  will),  to  stretch  out  and  to  curl  up  alternately,  while 
the  number  of  the  spreading  fingers  enables  the  animal  to 
grasp  a  comparatively  large  bulk  of  water  in  those  curling 
organs.  These,  then,  form  a  sieve ;  the  water  passes 
through  the  interstices  of  the  fingers,  while  the  tiny  atoms 
of  solid  matter,  or  the  equally  minute  animalcules  that 
constitute  the  food  of  the  Barnacle,  are  sifted  out,  and 
detained  by  the  fingers,  which,  curling  inward,  carry  what- 
ever is  captured  to  the  mouth. 

But  see  how  greatly  the  perfection  of  the  instrument  is 
promoted  by  the  projecting  hairs  with  which  every  one  of 
the  numerous  joints  is  beset.  These,  standing  out  at  right 
angles  (or  nearly  so)  to  the  direction  of  the  finger,  meet 
their  fellows  from  the  joints  of  the  next  finger,  and,  cross- 
ing their  points,  fill  the  interstices  with  an  innumerable 
series  of  finer  meshes, — meshes  of  such  delicacy  that  it  is 


BABNACLES.  195 

next  to  impossible  that  any  organised  body  inclosed  in  the 
given  area  should  escape. 

But  there  is  more  in  them  than  merely  this  minute  and 
wide-spread  ramification.  They  are,  as  we  have  seen, 
organs  of  touch  ;  so  that  the  net  has  not  only  the  mechani- 
cal power  of  capture,  common  to  an  inanimate  cast-net 
which  a  human  fisher  uses,  but  is  endowed  with  the  most 
exquisite  sensibility  in  every  part.  The  slightest  contact 
of  an  animalcule  in  the  inclosed  water  with  one  of  those 
thousands  of  sensitive  hairs  communicates  instantly  an 
impression  to  the  sensorium,  and  a  consciousness  of  the 
fact  to  the  Barnacle ;  who  is  thus,  without  doubt,  able 
with  the  quickness  of  thought  to  close  the  fingers  together 
at  that  part,  and  thus  secure  the  victim. 

To  make  use  of  the  prey  thus  secured,  the  Barnacle  is 
furnished  with  a  mouth,  which  can  be  protruded  into  a 
sort  of  wart,  and  is  provided  with  a  distinct  lip  bearing 
minute  palpi,  and  three  pairs  of  jaws,  of  which  the  outer 
two  are  horny  and  toothed,  while  the  innermost  is  soft 
and  fleshy. 

Fixed  and  immovable  as  the  Barnacles  are  in  their 
adult  and  final  stage,  they  have  passed  by  metamorphosis 
through  conditions  of  life  in  which  they  were  active,  roving 
h'ttle  creatures,  endowed  with  the  power  of  swimming 
freely  in  the  wide  sea.  In  this  condition  they  present  the 
closest  resemblance  to  familiar  forms  of  Crustacea,  as  you 
will  perceive  when  you  examine  some  specimens  of  the 
larvae  that  I  am  able  to  show  you. 

I  have  in  one  of  my  tanks  an  individual  of  the  fine  and 
large  Barnacle,  Balanus  porcatus,  which,  for  several  days 
past,  has  been  at  intervals  throwing  out  from  the  orifice  of 
its  shells  dense  clouds  of  atoms,  which  form  compact 
columns  reaching  from  the  animal  to  the  surface  of  the 
water.  One  of  these  cloudy  columns,  when  examined  with 
a  lens,  is  seen  to  be  composed  of  thousands  of  dancing 
creatures,  resembling  the  Water-fleas  that  we  lately  ex- 
o  2 


196  EVENINGS   AT    THE    MICROSCOPE. 

amined.  They  maintain  a  vivacious  motion,  and  yet  at 
the  same  time  keep  their  association  and  the  general  form 
of  the  column. 

Taking  out  a  few  of  the  dancing  atoms,  and  isolating 
them  in  this  glass  stage-cell,  we  see  that  they  have  exactly 
the  figure,  appearance,  and  character  of  the  young  of  the 
common  Cyclops ;  so  that  you  would,  without  hesitation,  if 
you  knew  nothing  of  their  parentage,  assign  them  to  that 
well'known  genus.  Their  movements  are  almost  incessant ; 
a  series  of  jerking  progressions,  performed  by  quick  but 
apparently  laborious  flappings  of  the  limbs,  right  and  left 
together.  They  occasionally  rest  from  their  exertions  for 
a  few  moments,  but  seem  to  have  no  power  of  alighting  on 
any  object. 

But,  in  order  to  obtain  a  more  precise  idea  of  the  struc- 
ture of  this  tiny  creature,  we  must  manage  to  restrain  its 
liberty  a  little,  by  applying  gentle  pressure  with  the  com- 
pressorium,  just  sufficient  to  confine  it  without  hurting  it. 
The  body  is  inclosed  in  a  broad  carapace,  shaped  much 
like  a  heraldic  shield,  but  very  convex  on  the  back,  and 
terminating  behind  in  a  slender .  point  or  spine,  which  is 
cut  into  minute  teeth  along  the  edges.  Below  this  shield 
is  seen  the  body,  with  three  pairs  of  legs,  a  great  proboscis 
in  the  middle  pointing  downwards  and  backwards,  and  the 
anal  fork,  which  consists  of  a  bulbous  base  and  two  diverg- 
ing points,  which  project  behind  under  the  spine  of  the 
shield. 

The  legs  are  exclusively  swimming  organs ;  they  have 
no  provision  for  grasping,  no  claws  or  hooks,  nor  do  they 
appear  to  be  capable  of  being  used  for  crawling  on  the 
ground  or  for  climbing  among  the  sea-weeds.  They  are 
fringed  along  one  edge  with  long  and  stout,  but  somewhat 
flexible,  spines,  of  which  those  that  are  nearest  the  trunk 
seem  more  rigid,  and  are  directed  more  at  right  angles  to 
the  limb  than  the  rest.  The  legs  are  formed  of  many 
imperfect  joints,  and  the  second  and  third  pairs  are 


BABNACLE8.  197 

double  from  the  basal  joint  outwards,  while  the  first 
pair  are  simple.  In  the  fore  part  of  the  body  a  large  eye 
is  placed,  deep-seated,  which  is  of  a  roundish  form,  and 
is  intensely  black  both  by  reflected  and  transmitted  light. 
On  the  summit  of  the  forehead  are  placed  a  pair  of  thick 
flexible  horn-like  organs,  which  are  abruptly  bent  in  the 
middle,  and  which  I  believe  represent  the  first  pair  of 
antennae.  This  then  is  the  first  stage  of  the  Barnacle, — 
the  form  under  which  it  appears  when  it  is  hatched  from 
the  egg. 


YODNO   OF  BAUNACLE. 


Among  the  multitudes  which  have  been  evolved  during 
these  last  few  days,  and  which  are  now  swimming  at  large 
in  the  tank,  we  may  be  able  to  detect  some  that  have 
passed  through  their  first  stage,  and,  having  moulted  their 
skin,  have  attained  a  more  advanced  form.  Here  is  one, 
which  by  its  superior  size  seems  to  have  made  some  pro- 
gress towards  maturity. 


198  EVENINGS    AT    THE    MICROSCOPE. 

Yes,  here  are  more.  These  are  evidently  in  their  second 
stage.  There  is  an  increase  in  length ;  for  whereas  the 
former  was  only  -nj^th  of  an  inch  in  length,  these  have 
attained  to  a  length  of  -^th  of  an  inch.  Yet  this  increase 
is  observable  in  no  other  dimension  than  that  of  total 
length,  and  this  is  due  to  the  development  of  the  terminal 
spine  of  the  shield,  which  is  now  much  produced,  and  cut 
into  minute  teeth.  The  anal  fork  is  also  attenuated, 
lengthened,  and  bent  abruptly  downward  at  the  base, 
where  it  is  very  mobile  ;  another  bend  in  the  middle 
throwing  the  extremity  into  the  horizontal  again.  The 
delicately  membranous  pouch-like  proboscis  is  more  clearly 
seen  beneath  the  breast,  the  extremity  of  which  is  directed 
backwards.  In  front  of  this  organ  there  are  two  decurved 
very  mobile  bristles,  set  on  pedicles,  or  stalks,  the  whole 
closely  resembling  the  internal  antennae  in  the  higher 
Crustacea.  The  lateral  horns  or  external  antennae  appear 
to  terminate  in  a  very  delicate  brush  of  hairs,  which  does 
not  seem  to  be  capable  of  being  protruded. 

The  little  animals  in  this  state  swim,  generally,  back 
downward ;  though  they  frequently  assume  a  perpendicular 
position,  both  direct  and  reversed.  I  see  them  now  occa- 
sionally resting  on  sea-weeds  and  Diatomacea,  though  the 
limbs  seem  even  worse  fitted  than  before  for  crawling, 
since  the  spines  or  bristles  with  which  they  are  fringed 
are  much  increased  in  length,  especially  on  the  third 
pair. 

A  specimen  nearly  twice  as  large  as  these  last  affords  us 
an  opportunity  of  tracing  the  Barnacle  to  another  point  of 
its  transformations.  The  modifications  are  chiefly  in  the 
proboscis  and  the  anal  fork.  The  former  now  points 
directly  downwards ;  is  furnished  with  a  pair  of  minute 
spines  on  its  anterior  side,  and  with  a  terminal  hook  ; 
while  its  posterior  side  is  set  with  strong  vibrating  cilia. 
The  anal  fork  is  greatly  increased  in  dimensions,  has  its 
edges  armed  with  spines  articulated  to  its  surface,  and  is 


BARNACLES.  199 

marked  with  longitudinal  lines  which  resemble  corruga- 
tions. The  under-surface  of  the  body  is  also  much  cor- 
rugated transversely. 

In  the  first  moult  the  spine  of  the  shield  was  greatly 
increased,  the  size  of  the  body  itself  remaining  stationary  ; 
in  the  second  moult  the  ratio  is  reversed,  the  body  has 
largely  increased,  but  the  spine  is  nearly  unchanged. 

We  cannot  follow  the  metamorphosis  any  farther  by 
personal  observations  ;  but  from  the  researches  of  others, 
and  especially  of  Mr.  Darwin,  we  know  that  other  stages 
have  to  be  passed  before  the  final  fixed  condition  is  at- 
tained. As  yet  no  perceptible  advance  has  been  made,  by 
either  of  the  two  moultings  which  we  have  traced,  from 
the  free,  jerking,  dancing  Water-flea  that  was  first  hatched, 
towards  the  sessile  Barnacle  inclosed  in  its  shelly  cone  of 
several  valves,  and  firmly  fixed  to  the  solid  rock  ;  and  we 
are  yet  at  a  loss  to  imagine  how  such  a  change  can  be 
effected. 

Nor  is  the  matter  apparently  helped  by  the  next  moult  ; 
for  though  there  now  ensues  a  great  change  of  form,  it 
does  not  seem  to  resemble  the  adult  Barnacle  much  (if  at 
all)  more  than  before.  If  described  without  reference  to 
its  parentage,  it  would  still  be  considered  an  Entomostra- 
cous*  Crustacean,  or  Water-flea,  but  removed  to  another 
tribe.  It  represents,  in  fact,  a  Cypris  ;  \  the  body  with  its 
fringed  limbs  being  now  included  within  two  convex  valves, 
like  those  of  a  mussel  or  other  bivalve  shell,  either  united 
by  a  hinge  along  the  back,  or  rather  soldered  together 
there,  so  as  only  to  allow  a  slight  opening  and  closing,  by 
the  elasticity  of  their  substance.  The  fore  part  of  the 
head  is  now  greatly  enlarged,  as  are  also  the  antennae, 


*  From  two  Greek  words  —  evropos  (entomos),  cut  up,  and 
(ostrakon),  a  shell.  A  term  applied  to  a  group  of  the  Crustaceans 
with  minute  bodies  very  much  divided  and  inclosed  in  a  shelly 
covering. 

t  See  figure  on  p.  181. 


200  EVENINGS   AT    THE    MICROSCOPE. 

which  project  from  the  shell.  The  single  eye  is  separated 
into  two,  which  are  large  and  attached  to  the  outer  arms 
of  two  hent  processes  placed  within  the  body,  in  the 
form  of  the  letters  UU.  The  legs  are  increased  by 
the  addition  of  two  pairs,  and  these  are  doubly  bent  in 
a  zig-zag  form,  and  can  be  protruded  from  between  the 
valves. 

It  is  a  highly  curious  fact  that  the  infant  Barnacle  has 
thus  passed  through  two  distinct  types  of  animal  life,  those 
of  the  Cyclops  and  the  Cypris.  These  are  not  one  type  in 
different  stages,  as  might  be  reasonably  presumed.  The 
young  of  Daphnia  and  of  Cyclops  are  so  much  alike,  that  it 
would  be  natural  to  presume  the  young  of  Cypris  to  be  of 
the  same  form ;  in  which  case,  we  should  .have  in  the 
young  Barnacle  merely  the  first  and  second  stages  of 
Cypris.  But  it  is  not  so.  Cypris  does  not  pass  through 
the  Cyclops  form  at  all ;  for,  according  to  Jurine,  the 
young  when  hatched  have  the  appearance  of  the  perfect 
animal,  though  varying  a  little  in  the  shape  of  their  shells. 

It  is  in  this  second  form,  which  may  be  considered  the 
pupa  of  the  Barnacle,  that  the  animal  quits  its  free,  roving 
life,  and  becomes  a  fixture  for  the  remainder  of  its  days. 
And  this  is  a  most  wonderful  process ;  so  wonderful,  that 
it  would  be  utterly  incredible,  but  that  the  researches  of 
Mr.  Darwin  have  proved  it  incontestably  to  be  the  means 
by  which  the  wisdom  of  God  has  ordained  that  the  little 
Water-flea  should  be  transformed  into  a  stony  Acorn 
Barnacle. 

Having  selected  a  suitable  place  for  fixing  its  residence, 
such  as  those  massive  rocks  which  sustain  the  impetuous 
billows  on  our  sea-worn  coasts,  the  great  projecting 
antennae  manifest  a  new  and  unprecedented  function. 
Glands  situated  at  their  base  secrete  a  tenacious  glue, 
which,  being  poured  out  in  great  profusion,  cements  the 
whole  front  of  the  head  to  the  rock,  including  and  con- 
cealing the  antennae  themselves.  The  cement  rapidly 


BABNACLES.  201 

sets  under  water,  and  the  animal  is  henceforth  immov- 
able. 

It  now  moults  its  skin  once  more.  Another  great 
change  takes  place  ;  the  bivalve  shell  is  thrown  off,  as  are 
also  the  eyes  with  their  bent  supports,  and  it  is  seen  to  be 
a  true  Barnacle,  though  as  yet  of  minute  dimensions,  and 
with  its  valves  in  a  very  rudimentary  condition.  It  is 
now  the  representative  of  a  third  type  among  the  Crusta- 
cean forms,  for  it  is  in  effect  a  Stomapod ;  *  such  as  the 
Opossum  Shrimp  (My sis),  for  example,  with  the  shield 
composed  of  several  pieces,  stony  in  texture,  on  account  of 
the  great  development  of  their  calcareous  element,  and  so 
modified  in  form  as  to  make  a  low  cone,  the  legs  (become 
the  cirri,  or  whafc  I  have  above  called  the  "  fingers  ") 
made  to  perform  their  movements  backwards  instead  of 
forwards,  and  the  whole  abdomen  reduced  to  an  almost 
invisible  point. 

Marvellous  indeed  are  these  facts.  If  such  changes  as 
these,  or  anything  approaching  to  them,  took  place  in  the 
history  of  some  familiar  domestic  animal, — if  the  horse, 
for  instance,  were  invariably  born  under  the  form  of  a  fish, 
passed  through  several  modifications  of  this  form,  imitating 
the  shape  of  the  perch,  then  the  pike,  then  the  eel,  by 
successive  castings  of  its  skin ;  then  by  another  shift  ap- 
peared as  a  bird  ;  and  then,  glueing  itself  by  its  forehead  to 
some  stone,  with  its  feet  in  the  air,  threw  off  its  covering 
once  more,  and  became  a  foal,  which  then  gradually  grew 
into  a  horse ; — or  if  some  veracious  traveller,  some  Living- 
stone or  Barth,  were  to  tell  us  that  such  processes  were 
the  invariable  conditions  under  which  some  beast  of  burden, 
largely  used  in  the  centre  of  Africa,  passed, — should  we 
not  think  them  very  wonderful  ?  Yet  they  would  not  be  a 
whit  more  wonderful  in  this  supposed  case  than  in  the  case 

*  From  the  Greek  <rro/xa  (stoma),  mouth,  and  irovs  (pous),  foot.  A 
name  given  to  those  Crustaceans  which  have  proper  feet  near  the 
mouth. 


202  EVENINGS    AT    THE    MICROSCOPE. 

of  the  Barnacle,  in  whose  history  they  are  constantly  ex- 
hibited in  millions  of  individuals,  and  have  been  for  ages  ; 
even  in  creatures  so  common  that  we  cannot  take  a 
walk  beneath  our  sea-cliffs,  without  treading  on  them  by 
hundreds  ! 


SPIDERS    AND    MITES.  203 


CHAPTER 

SPIDERS    AND    MITES. 

SPIDERS,  I  am  sure,  are  not  favourites  with  you.  With 
the  exception  of  the  poor  prisoner  in  the  Bastille,  who  had 
succeeded  in  taming  a  Spider, — the  only  creature  besides 
himself  that  inhabited  his  dungeon, — I  do  not  think  I 
have  ever  heard  of  any  one  who  loved  or  admired  Spiders 
morally.  Yet,  physically,  we  may  find  much  to  admire  in 
them,  as  not  a  few  naturalists  have  done  before  us ;  there 
are  men  who  have  devoted  their  lives  to  the  study  of  this 
unamiable  race  ;  and  who  have  discovered  in  them  the 
same  wondrous  skill,  and  the  same  perfect  adaptation  of 
organ  to  function,  of  structure  to  habit,  that  mark  all 
God's  works,  whether  we  think  them  pretty  or  ugly, 
amiable  or  repulsive. 

I  am  going  to  show  you  some  of  these  pieces  of  mechan- 
ism. Remember  that  the  whole  tribe  is  sent  into  the 
world  to  perform  one  business  :  they  are  commissioned 
to  keep  down  what  would  otherwise  be  a  "  plague  of  flies." 
They  are  fly-butchers  by  profession  ;  and,  just  as  our  beef- 
and  mutton-butchers  have  their  slaughter-house,  their 
steel,  their  knives,  their  pole-axe,  their  hooks,  so  are 
these  little  slaughterers  furnished  with  nets  and  traps, 
with  caves,  with  fangs,  and  hooks,  and  poison-bags,  ready 
for  their  constant  work.  They  have,  in  fact,  nothing  else 
to  do :  their  whole  lives  are  spent  in  slaughtering, — with 
the  exception  of  rearing  fresh  generations  of  slaughterers, 
— and  I  suppose  they  think,  and  are  intended  to  think,  of 
nothing  else. 


204  EVENINGS   AT    THE    MICROSCOPE. 

I  was  one  day  in  an  omnibus,  in  the  corner  of  which 
sat  a  butcher.  Presently  a  man  got  in,  whose  blue  ging- 
ham coat  indicated  the  same  trade.  He  seated  himself 
opposite  the  other,  and  the  two  were  soon  in  conversation. 
"  Do  you  know  Jackson?"  says  A.  "No,"  says  B; 
"  where  does  he  slaughter?"  The  reply  gave  me  anew 
idea ;  he  evidently  considered  that  "  slaughtering  "  was 
the  only  occupation  worthy  of  a  man,  and  therefore  the 
only  one  worthy  of  man's  thought.  Spiders  are  just  the 
same.  If  an  Epeira  met  a  Clubiona,  probably  the  first 
interchange  of  civilities  would  be  something  like — "  Where 
do  you  slaughter  ?  " 

"  No  one,"  says  Professor  Bymer  Jones,  "  who  looks' at 
the  armature  of  a  Spider's  jaws  can  mistake  the  intention 
with  which  this  terrible  apparatus  was  planned.  '  Murder  ' 
is  engraved  legibly  on  every  piece  that  enters  into  its  com- 
position." But  surely  the  Professor  is  rather  severe.  I 
do  not  think  this  paragraph  was  written  on  an  autumn 
morning,  when  the  flies  had  driven  him  out  of  bed  prema- 
turely early,  by  incessantly  alighting  on  his  nose  ;  nor  on 
coming  home  from  a  summer  evening's  walk  through  the 
marsh,  where  clouds  of  singing  and  stinging  gnats  had 
been  the  only  objects-  of  cognisance  to  sight,  hearing,  and 
feeling.  If  so,  he  would  have  been  ready  to  pronounce 
"  killing  no  murder,"  and  have  blessed  the  slaughtering 
Spiders  as  pursuing  a  most  praiseworthy  and  useful  occu- 
pation. Circumstances  change  opinions. 

We  will  not,  then,  touch  the  moral  question ;  but  just 
look  at  this  apparatus  from  the  head  of  one  of  our  common 
Spiders  (Clubiona  atrox),  a  long-legged  and  swift  species, 
that  builds  a  compact  cloth-like  web  in  our  out-houses, 
with  a  gallery  open  at  each  end  for  retreat  in  danger. 
The  specimen  is  a  part  of  the  slough  or  cast  skin,  which 
you  may  always  find  in  the  neighbourhood  of  such  a  web  ; 
and  it  is  particularly  suitable  for  examination,  because  it 
is  sloughed  in  the  most  perfect  condition  ;  every  part,  the 


SPIDEES    AND    MITES.  205 

fangs,  the  palps,  the  legs,  with  all  their  joints,  the  corneas 
of  the  eyes,  the  entire  skin  with  every  hair, — all  are  here, 
and  all  in  their  places,  with  a  cleanness  and  translucency 
which  it  would  require  much  skill  in  dissection  to  obtain, 
if  we  captured  a  living  Spider  for  our  purpose. 

There  are  in  front  of  the  head  two  stout  brown  organs, 
which  are  the  representatives  of  the  antennaB  in  insects ; 
though  very  much  modified  both  in  form  and  function. 
They  are  here  the  effective  weapons  of  attack.  Each 
consists  of  two  joints :  the  basal  one,  which  forms  the 
most  conspicuous  portion  of  the  organ,  and  the  terminal 
one,  which  is  the  fang.  The  former  is  a  thick  hollow  case, 
somewhat  cylindrical,  but  flattened  sidewise,  formed  of 
stiff  chitine,  covered  with  minute  transverse  ridges  on  its 
whole  surface,  like  the  marks  left  on  the  sand  by  the 
rippling  wavelets,  and  studded  with  stout  coarse  black 
hair.  Its  extremity  is  cut  off  obliquely,  and  forms  a 
furrow,  the  edges  of  which  are  beset  with  polished  conical 
points,  resembling  teeth. 

To  the  upper  end  of  this  furrowed  case  is  fixed  by  a 
hinge-joint  the  fang,  which  is  a  curved  claw-like  organ, 
formed  of  hard  chitine,  and  consisting  of  two  parts,  a 
swollen  oval  base,  which  is  highly  polished,  and  a  more 
slender  tip,  the  surface  of  which  has  a  silky  lustre,  from 
being  covered  with  very  fine  and  close- set  longitudinal 
grooves.  This  whole  organ  falls  into  the  furrow  of  the 
basal  joint,  when  not  in  use,  exactly  as  the  blade  of  a 
clasp-knife  shuts  into  the  haft ;  but,  when  the  animal  is 
excited,  either  to  defend  itself  or  to  attack  its  prey,  the 
fang  becomes  stiffly  erected. 

By  turning  the  object  on  its  axis,  and  examining  the 
extreme  tip  of  the  fang,  we  see  that  it  is  not  brought  to  a 
fine  point,  but  that  it  has  the  appearance  of  having  been 
cut  off  slant- wise  just  at  the  tip  ;  and  that  it  is  tubular. 
Now  this  is  a  provision  for  the  speedy  infliction  of  death 
upon  the  victim  ;  for  both  the  fang  and  the  thick  basal 


206  EVENINGS    AT    THE    MICROSCOPE. 

joint  are  permeated  by  a  slender  membranous  tube,  which 
is  the  poison  duct,  and  which  terminates  at  the  open 
extremity  of  the  former,  while  at  the  other  end  it  commu- 
nicates with  a  lengthened  oval  sac  where  the  venom  is 
secreted.  This,  of  course,  we  do  not  see  here,  for  it  is 
not  sloughed  with  the  exuviae,  but  retained  in  the  interior 
of  the  body;  but  in  life  it  is  a  sac,  extending  into  the 
cephalo-thorax, — as  that  part  of  the  body  which  carries 
the  legs  is  called, — and  covered  with  spiral  folds  pro- 
duced by  the  arrangement  of  the  fibres  of  its  contractile 
tissue. 

When  the  Spider  attacks  a  fly,  it  plunges  into  its 
victim  the  two  fangs,  the  action  of  which  is  downwards, 
and  not  from  right  to  left,  like  that  of  the  jaws  of  insects. 
At  the  same  instant  a  drop  of  poison  is  secreted  in  each 
gland,  which,  oozing  through  the  duct,  escapes  from  the 

perforated  end  of  the 
fang  into  the  wound,  and 
rapidly  produces  death. 
The  fangs  are  then  clasped 
down,  carrying  the  prey, 
which  they  powerfully 
press  against  the  toothed 
FANG  OF  SPIDER.  edges  of  the  stout  basal 

piece,  by  which  means  the  nutritive  fluids  of  the  prey  are 
pressed  out,  and  taken  into  the  mouth,  the  dried  and 
empty  skin  being  rejected.  The  poison  is  of  an  acid 
nature,  as  experiments  performed  with  irritated  spiders 
prove  ;  litmus  paper  pierced  by  them  becoming  red  as  far 
round  the  perforations  as  the  emitted  fluid  spreads. 

In  the  slough,  the  upper  surface  of  the  cephalo-thorax 
is  always  detached  as  a  thin  plate,  convex  outwardly,  con- 
cave inwardly.  As  it  is  upon  the  front  portion  of  this 
division  of  the  body  that  the  eyes  are  situate,  the  slough 
displays  these  with  great  clearness  and  beauty  beneath  the 
microscope.  Here  you  may  see  them.  The  whole  slough 


SPIDEBS    AND    MITES.  207 

from  its  thinness  is  semi-pellucid,  but  the  eyes  transmit 
the  light  with  brilliance,  not,  however,  as  if  they  were 
simple  round  holes,  because  you  can  discern  very  mani- 
festly a  hemispherical  glassy  coat,  by  which  it  is  refracted. 
It  is,  however,  when  we  examine  the  forehead  of  a  living 
or  recently  killed  spider,  that  we  see  the  eyes  to  advan- 
tage. In  this  example  of  the  same  species  (Clubiona 
atrox),  you  see  them,  like  polished  globes  of  diamond, 
sunk  into  the  solid  skin  of  the  head.  Their  form  is 
unimpeachably  perfect,  and  the  reflection  of  light  from 
their  surface  most  brilliant. 


EYES   OF    SPIDER. 


The  arrangement  of  these  lustrous  eyes  is  worthy  of 
attention.  They  are  generally  eight  in  number  in  Spiders, 
but  their  relative  position  varies  so  much,  as  to  afford 
good  characters  by  which  naturalists  have  grouped  them 
in  genera.  In  the  Clubiona  which  we  have  been  examin- 
ing, they  are  placed  in  two  nearly  straight  transverse  rows 
on  the  forehead ;  but  as  this  surface  is  convex,  it  follows 
that  the  axis  of  every  eye  points  in  a  different  direction 
from  that  of  its  fellows.  In  Epeira,  on  the  other  hand, 
represented  by  our  great  Garden  Spider,  so  commonly  seen 


208  EVENINGS    AT    THE    MICROSCOPE. 

in  the  centre  of  its  perpendicular  web,  on  shrubs  and  in 
corners  of  our  gardens,  the  four  middle  eyes  form  a  square, 
and  the  two  lateral  ones  on  each  side  are  placed  in  contact 
with  each  other. 

It  is  interesting  to  remark  that  their  arrangement  is  not 
arbitrary,  but  is  ancillary  to  the  varying  instincts  and 
wants  of  the  different  kinds.  On  this  subject  I  will  quote 
to  you  what  Professor  Owen  says  : — "  The  position  of 
the  four  median  ones  is  the  most  constant ;  they  gene- 
rally indicate  a  square  or  trapezium,  and  may  be  com- 
pared with  the  median  ocelli  in  hexapod  insects.  The 
two,  or  the  two  pairs  of  lateral  ocelli  may  be  compared 
with  the  compound  eyes  of  insects ;  the  anterior  of  these 
has  usually  a  downward  aspect,  whilst  the  posterior  looks 
backwards  ;  the  variety  in  the  arrangement  of  the  ocelli  of 
Spiders  always  bears  a  constant  relation  to  the  general 
conformation  and  habits  of  the  species.  Dujes  has 
observed  that  those  Spiders  which  hide  in  tubes,  or  lurk 
in  obscure  retreats,  either  underground  or  in  the  holes  or 
fissures  of  walls  or  rocks,  from  which  they  only  emerge  to 
seize  a  passing  prey,  have  their  eyes  aggregated  in  a  close 
group  in  the  middle  of  the  forehead,  as  in  the  Bird-spider, 
the  Clotho,  &c.  The  Spiders  which  inhabit  short  tubes, 
terminated  by  a  large  web  exposed  to  the  open  air,  have 
the  eyes  separated,  and  more  spread  upon  the  front  of  the, 
cephalo-thorax.  Those  Spiders  which  rest  in  the  centre  of 
a  free  web,  and  along  which  they  frequently  traverse,  have 
the  eyes  supported  on  slight  prominences  which  permit  a 
greater  divergence  of  their  axes  ;  this  structure  is  well 
marked  in  the  genus  Thomisa,  the  species  of  which  lie  in 
ambuscade  in  flowers.  Lastly,  the  spiders  called  Ermntes, 
or  wanderers,  have  their  eyes  still  more  scattered,  the 
lateral  ones  being  placed  at  the  margins  of  the  cephalo- 
thorax."" 

The  shining  hemisphere  (or  nearly  a  sphere)  is  in  each 
*  "  Comp.  Anat."  (Ed.  2),  451. 


SPIDERS   AND   MITES.  209 

case  covered  with  a  thick  cornea,  a  continuation  of  the 
skin,  perfectly  transparent,  and  throwing  off  its  outer  coats 
successively  in  the  process  of  moulting,  like  that  of  the 
rest  of  the  body.  The  centre  of  its  inner  surface  is  deeply 
excavated  for  the  reception  of  a  crystalline  lens,  which  is 
globular  in  form,  and  which  rests  behind  on  the  front  sur- 
face of  a  hemispherical  vitreous  body,  without  sinking  into 
jt.  The  space  between  this  body  and  the  sides  of  the  lens 
forms  a  ring-like  channel  which  is  filled  with  an  aqueous 
humour,  and  into  this  projects  a  circular  process  of  the 
thick  pigment-coat,  which  corresponds  to  the  choroid,  thus 
defining  the  pupil  of  the  eye,  and  at  the  same  time  con- 
fining the  lens  to  its  proper  situation.  The  margin  of  this 
pigment-ring  may  be  considered  as  an  iris,  and  is  of 
various  colours,  as  red,  green,  or  brown,  in  those  species 
which  are  active  by  daylight,  while  it  is  black  at  the  back 
of  the  eye.  The  nocturnal  species  have  no  dark  pigments, 
but  are  furnished  with  a  curtain  (tapetum),  which  reflects 
a  brilliant  metallic  lustre,  and  makes  the  eyes  of  these 
Spiders  glare  in  the  twilight,  like  those  of  cats. 

It  will  be  interesting  to  compare  with  this  range  of 
eyes,  the  same  organs  in  a  kindred  animal,  the  common 
Harvestman  (Phalangium  cornutum).  Here  in  the  centre 
of  the  cephalo-thorax  rises  a  short  pillar,  which  is 
crowned  with  two  rows  of  conical  points,  with  polished 
black  tips.  On  each  side  of  the  pillar  is  a  large  black  eye, 
hemispherical  in  form  and  brilliantly  glossy,  exactly 
resembling,  indeed,  those  which  we  have  just  examined. 
There  are,  however,  only  this  single  pair  which  thus  look 
out  laterally,  exactly  like  the  eyes  of  Birds.  There  is, 
indeed,  a  speck  on  each  side  of  the  thorax,  considerably 
removed  from  the  eye -pillar,  just  above  the  origin  of  the 
first  pair  of  legs,  which  has  been  mistaken  for  an  eye ; 
but  it  is  truly  a  spiracle,  or  breathing-hole. 

There  are  many  other  points  of  interest  about  this  Har- 
vestman, such  as  the  conical  spines  which  stud  the  head, 


210  EVENINGS   AT    THE    MICROSCOPE. 

body,  and  limbs ;  the  multitude  of  small  bead-like  joints 
into  which  the  foot  (tarsus)  is  divided ;  and  in  particular 
the  hammer-like  form  of  the  modified  antennae,  which  bend 
abruptly  downwards,  and  have  pincer-tips.  These  are 
highly  curious,  and  you  may  examine  them  at  your  lei- 
sure ;  but  for  the  present  we  will  return  to  our  Spiders. 

Ever  since  those  mythic  times  when  Arachne  contended 
with  Minerva  for  supremacy  in  needlework,  and  was 
changed,  for  her  pains,  into  a  spider,  our  little  spinners 
have  been  famous  (Spider  =  ^p-inne)  for  their  matchless 
achievements  in  thread.  And  still  their  industrious  art  is 
plied  everywhere  around  us  ;  in  our  chambers,  in  our 
windows,  in  our  cellars,  in  our  walls,  in  our  gardens,  in 
waste  and  desert  places,  and  even  under  water.  But  you 
shall  hear  what  Professor  Owen  says  on  the  degree  and 
mode  in  which  Spiders  exercise  their  singular  secreting 
faculty,  which  "varies  considerably  in  the  different  species. 
Some,  as  the  Clubionce,  line  with  silk  a  conical  or  cylin- 
drical retreat,  formed,  perhaps,  of  a  coiled-up  leaf,  and 
having  an  outlet  at  both  extremities,  from  one  of  which 
may  issue  threads  to  entrap  their  prey.  Others,  as  the 
Segestria,  fabricate  a  silken  burrow  of  five  or  six  inches  in 
length,  in  the  cleft  of  an  old  wall.  The  Mygale  cemetaria 
lines  a  subterraneous  burrow  with  the  same  substance,  and 
manufactures  a  close-fitting  trap-door  of  cemented  earth, 
lined  with  silk,  and  so  attached  to  the  entry  of  the  burrow 
as  to  fall  down  and  cover  it  by  its  own  weight,  and  which 
the  inmate  can  keep  close  shut  by  means  of  strong  attached 
threads. 

"  The  arrangement  of  Spiders  by  Mr.  Walckenaer  into 
families,  characterised  by  their  habits,  places  the  principal 
varieties  of  their  webs  in  a  very  concise  point  of  view. 

"  The  Cursores,  Saltatores,  and  Laterigrad®,  make  no 
webs  :  the  first  catch  their  prey  by  swift  pursuit ;  the 
second  spring  upon  their  prey  by  insidious  and  agile 
leaps ;  the  third  run,  crab-like,  sideways  or  backwards, 


SPIDEES  AND  MITES.  211 

and  occasionally  throw  out  adhesive  threads  to  entrap 
their  prey.  The  Latebricola  hide  in  burrows  and  fissures, 
which  they  line  with  a  web.  The  Tubicola  inclose  them- 
selves in  a  silken  tube,  strengthened  externally  by  leaves 
or  other  foreign  substances.  The  Niditela  weave  a  nest, 
whence  issue  threads  to  entrap  their  prey.  The  Filitela 
are  remarkable  for  the  long  threads  of  silk  which  they 
spread  about  in  the  places  where  they  prowl  in  quest  of 
prey.  The  Lapitela  spin  great  webs  of  a  close  texture, 
like  hammocks,  and  wait  for  the  insects  that  may  be 
entangled  therein.  The  Orbitela  spread  abroad  webs 
of  a  regular  and  open  texture,  either  circular  or  spiral, 
and  remain  in  the  middle  or  on  one  side,  in  readiness  to 
spring  upon  an  entangled  insect.  The  Retitela  spin  webs 
of  an  open  mesh-work,  and  of  an  irregular  form,  and 
remain  in  the  middle  or  on  one  side,  to  seize  their  prey. 
Lastly,  the  Aquitela  spread  their  silken  filaments  under 
water,  to  entrap  aquatic  insects. 

11  The  silken  secretion  of  Spiders  is  not  applied  only  to 
the  formation  of  a  warm  and  comfortable  dwelling  for 
themselves,  or  of  a  trap  for  their  prey ;  it  is  often  em- 
ployed to  master  the  struggles  of  a  resisting  insect,  which 
is  bound  round  by  an  extemporary  filament,  spun  for  the 
occasion,  as  by  a  strong  cord.  It  forms  the  aeronautic 
filament  of  the  young  migratory  brood.  It  serves  to 
attach  the  moulting  Hydrachna  to  an  aquatic  plant  by  the 
anterior  part  of  the  body,  when  it  struggles  to  withdraw 
itself  from  its  exuvium.  Lastly,  a  softer  and  more  silken 
kind  of  web  is  prepared  for  the  purpose  of  receiving  the 
eggs  and  to  serve  as  a  nest  for  the  young."  * 

The  silk  with  which  these  various  fabrics  are  con- 
structed is  a  thick,  viscous,  transparent  liquid,  much  like 
a  solution  of  gum  arabic,  which  hardens  quickly  on  expo- 
sure to  the  air,  but  can  meanwhile  be  drawn  out  into 
thread.  So  far,  it  agrees  with  the  silk  of  the  silkworm 

*  Owen,  "  Comp.  Anat"  (Ed.  2),  458. 


212  EVENINGS    AT    THE    MICROSCOPE. 

and  other  caterpillars ;  but  the  apparatus  by  which  it  is 
secreted,  and  that  by  which  it  is  spun,  are  both  far  more 
complex  and  elaborate  than  those  of  the  latter.  Generally 
speaking,  there  are  three  pairs  of  spinnerets,  or  external 
organs,  through  which  the  threads  are  produced ;  but  in 
some  few  cases  there  are  only  two  pairs,*  and  in  others, 
as  the  Garden  Spiders  (Epeira),  the  hindmost  pair  seem 
to  be  united  into  a  single  spinneret.  These  are  always 
situated  at  the  hinder  extremity  of  the  body,  and  I  will 
show  them  to  you  presently.  First,  however,  I  will  de- 
scribe the  internal  apparatus ;  the  source  of  the  threads. 

The  glands  which  secrete  the  gummy  fluid  are  placed  in 
the  midst  of  the  abdominal  viscera,  and  in  some  instances 
— as  in  the  female  of  Epeira  fasciata,  a  species  which 
makes  a  remarkably  large  web — they  occupy  about  a 
quarter  of  the  whole  bulk  of  the  abdomen.  About  five 
different  kinds  of  these  glands  may  be  distinguished, 
though  they  are  not  all  present  in  every  species.  The 
Epdra,  however,  present  them  all. 

In  this  genus  there  are  : — 1.  Small,  pear-shaped  bags, 
associated  in  groups  of  hundreds,  and  leading  off  by 
short  tubes,  which  are  interlaced  in  a  screw-like  manner, 
and  open  in  all  of  the  spinnerets.  2.  Six  long  twisted 
tubes,  which  gradually  enlarge  into  as  many  pouches,  and 
then  are  each  protracted  into  a  very  long  duct,  which 
forms  a  double  loop.  3.  Three  pairs  of  glandular  tubes, 
similar  to  the  preceding,  but  which  open  externally  through 
short  ducts.  4.  Two  groups  of  much-branched  sacs,  whose 
long  ducts  run  to  the  upper  pair  of  spinnerets.  5.  Two 
slightly-branched  blind -tubes,  which  terminate  by  two 
short  ducts  in  the  middle  pair  of  spinnerets. | 

It  is  not  very  easy  to  examine  the  spinnerets  with  a 

*  "  There  is  a  fourth  pair  in  Mr.  BlackwalPs  family  of  the  Cini- 
flvridce,  situate  in  front  of  the  ordinary  anterior  pair."  (Meade.) 

f  See  a  valuable  account,  by  Mr.  R.  H.  Meade,  of  the  secreting  glands 
in  Spiders,  and  of  the  distinct  functions  of  the  various  kinds  of  these 
organs,  read  at  the  British  Association,  Sept.  25th,  1858. 


SPIDERS    AND    MITES.  213 

microscope,  so  as  to  make  out  their  structure.  If  we 
confine  the  Spider  in  a  glass  cell,  it  is  so  restless  that  the 
least  shock  or  change  of  position  will  cause  it  to  move  to 
and  fro ;  and,  besides,  when  it  does  become  quiescent,  the 
spinnerets  are  closed  in  towards  each  other,  so  that  we 
cannot  see  their  extremities.  By  selecting  a  specimen, 
however,  recently  killed,  such  as  this  Clubiona,  we  may 
discern  sufficient  to  enable  us  to  comprehend  their  con- 
struction. 

Looking,  then,  at  the  abdomen  from  beneath,  we  see 
the  three  pairs  of  spinnerets  clustered  together  close  to 
the  extremity.  The  pair  most  forward  are  shaped  some- 
what like  barrels,  whose  free  ends  bend  over  toward  each 
other.  They  are  covered  with  stiff  black  hairs,  and  just 
within  the  margin  of  what  may  be  called  the  head  of  the 
barrel  (for  it  is  cut  off  horizontally,  with  a  sharp  rim), 
there  is  a  circle  of  very  close-set,  stiff,  whitish  bristles, 
which  arch  inwards.  The  whole  flat  surface  of  the  "  head," 
within  this  circle  of  bristles,  is  beset  with  very  minute 
horny  tubes,  standing  erect,  which  are  the  outlets  of  the 
silk- ducts  that  belong  to  this  pair. 

Behind  this  first  pair  are  seen  the  middle  pair,  almost 
concealed,  however,  from  their  shortness  and  smallness, 
and  from  the  approximation  of  the  first  and  third  pairs. 
We  can  discern  that  they  are  more  teat-like  than  the  pre- 
ceding, terminating  in  a  minute  wart,  which  is  prolonged 
into  a  horny  tube.  The  whole  teat  is  set  with  similar 
tubes,  which  are  larger  and  longer  than  those  of  the  first 
pair.  Finally,  the  third  pair  resemble  palpi,  for  each  con- 
sists of  two  lengthened  joints,  and  are  bluntly  pointed. 
The  spinning  tubes  in  these  are  limited,  as  it  appears  to 
me,  to  one  or  two  at  the  extreme  end  of  each  spinneret, 
the  whole  surface  besides  being  covered  with  the  ordinary 
long  bristles.  Strictly  speaking,  however,  they  are  three- 
jointed,  for  all  the  spinnerets  spring  from  wart-like  sockets, 
which  may  be  considered  as  basal  joints ;  and  as  the 


214  EVENINGS   AT   THE    MICROSCOPE. 

circlet  of  bristles  in  the  first  pair  doubtless  indicates  a 
short  joint,  sunken  as  it  were  within  the  preceding,  this 
pair  is  likewise  three-jointed  ;  the  middle  pair  appears  to 
be  but  two-jointed. 

The  minute  horny  tubes  are  themselves  composed  of 
two  joints,  the  basal  one  thick,  the  terminal  one  very 
slender,  and  perforated  with  a  very  minute  orifice,  through 
which  the  gum  oozes  at  the  will  of  the  animal  as  an 
equally  attenuated  thread.  On  our  Clubiona,  the  number 
of  tubes  in  all  the  spinnerets  is  about  three  hundred  ;  but 
in  the  Garden  Spider  (Epdrd)  they  exceed  a  thousand. 

This  remarkable  multiplicity  of  the  strands  with  which 
the  apparently  simple  and  certainly  slender  thread  of  the 
Spider  is  composed,  has  attracted  the  attention  of  those 
philosophers  who  seek  to  discover  the  reasons  of  the  phe- 
nomena they  see  in  nature.  The  explanation  was  first 
suggested,  I  believe,  by  Mr.  Rennie,*  but  it  has  been 
amplified  with  much  force  by  Professor  Jones,  in  the  follow- 
ing words : — 

"A  very  obvious  reflection  will  here  naturally  suggest 
itself  in  connexion  with  this  beautful  machinery;  why, 
in  the  case  of  the  Spider,  it  has  been  found  necessary  to 
provide  a  rope  of  such  complex  structure,  when  in  so 
many  Insects  a  simple,  undivided  thread,  drawn  from  the 
orifice  of  a  single  tube,  like  the  thread  of  the  silkworm, 
for  instance,  was  sufficient  for  all  required  purposes.  And 
here,  as  in  every  other  case,  it  will  be  found  on  considera- 
tion, that  a  complicated  apparatus  has  been  substituted 
for  a  simple  one  only  to  meet  the  requirements  of  strict 
necessity.  The  slow-moving  caterpillar,  as  it  leisurely 
produces  its  silken  cord,  gives  time  enough  for  the  fluid  of 
which  it  is  formed  to  harden  by  degrees  into  a  tenacious 
filament,  as  it  is  allowed  to  issue  by  instalments  from  the 
end  of  the  labial  pipe ;  but  the  habits  of  the  Spider  re- 
quire a  very  different  mode  of  proceeding,  as  its  line  must 

*  "Insect  Architecture,"  337. 


SPIDERS    AND    MITES.  215 

be  instantly  converted  from  a  fluid  into  a  strong  rope, 
or  it  would  be  of  no  use  for  the  purposes  it  is  intended  to 
fulfil.  Let  a  fly,  for  example,  become  entangled  in  the 
meshes  of  a  Spider's  web ;  no  time  is  to  be  lost ;  the 
struggling  victim,  by  every  effort  to  escape,  is  tearing 
the  meshes  that  entangle  it,  and  would  soon  succeed  in 
breaking  loose  did  not  its  lurking  destroyer  at  once  rush 
out  to  complete  the  capture  and  save  its  net,  spun  with  so 
much  labour,  from  ruin.  With  the  rapidity  of  thought,  it 
darts  upon  its  prey,  and  before  the  eye  of  the  spectator 
can  comprehend  the  manoeuvre,  the  poor  fly  is  swathed  in 
silken  bands,  until  it  is  as  incapable  of  moving  as  an 
Egyptian  mummy.  To  allow  the  Spider  to  perform  such 
a  feat  as  this,  its  thread  must  evidently  be  instantaneously 
placed  at  its  disposal,  which  would  have  been  impossible 
had  it  been  a  single  cord,  but  being  subdivided  into 
numerous  filaments,  so  attenuated  as  we  have  seen  them 
to  be,  there  is  no  time  lost  in  the  drying ;  from  being 
fluid  they  are  at  once  converted  into  a  solid  rope,  ready 
for  immediate  service."  * 

No  doubt  you  have  often  admired  the  exquisite  regu- 
larity of  those  Spiders'  webs  which  are  called  geometric ; 
that  of  our  abundant  Garden  Spider,  for  instance.  You 
have  observed  the  cables  which  stretch  from  wall  to  wall, 
or  from  bush  to  bush,  in  various  directions,  to  form  the 
scaffolding,  on  which  the  net  is  afterwards  to  be  woven ; 
then  you  have  marked  the  straight  lines,  like  the  spokes 
of  a  wheel,  that  radiate  from  the  centre  to  various  points 
of  these  outwork  cables,  and  finally  the  spiral  thread  that 
circles  again  and  again  round  the  radii,  till  an  exquisite 
net  of  many  meshes  is  formed. 

But  possibly  you   are  not  aware  that  these  lines  are 

formed  of  two  quite  distinct  sorts  of  silk.     It  has  been 

shown  that  the  cables  and  radii  are  perfectly  unadhesiye, 

while  the  concentric  or  spiral  circles  are  extremely  viscid. 

*  «  Nat.  Hist  of  Anun.,"  ii.  339. 


216  EVENINGS    AT    THE    MICROSCOPE. 

Now  the  microscope,  or  a  powerful  lens,  will  reveal  the 
cause  of  this  difference ;  the  threads  of  the  cables  and 
radii  are  perfectly  simple,  while  the  spiral  threads  are 
closely  studded  with  minute  globules  of  fluid,  like  drops 
of  dew,  which,  from  the  elasticity  of  the  thread,  are 
easily  separated  from  each  other.*  These  are  globules  of 
viscid  gum,  as  is  easily  proved  by  touching  one  or  two 
with  the  finger,  to  which  they  will  instantly  adhere ;  or  by 
throwing  a  little  fine  dust  over  the  nets,  when  the  spirals 
will  be  found  clogged  with  dirt,  while  the  radii  and  cables 
remain  unsoiled.  It  is  these  viscid  threads  alone  that 
have  the  power  of  detaining  the  vagrant  flies  which  acci- 
dentally touch  the  net. 

The  diversity  in  the  secreting  organs  already  alluded  to, 
as  well  as  in  the  spinnerets,  is  no  doubt  connected  with 
this  difference  in  the  character  of  the  silk  ;  and  it  is 
worthy  of  remark,  that  this  diversity  is  greatest  in  such 
Spiders  as  the  Upeirce,  which  spin  geometric  nets. 

Immense  is  the  number  of  globules  of  viscidity  that 
stud  the  spiral  circles  of  one  of  these  nets.  Mr.  Blackwall, 
the  able  and  learned  historian  of  the  tribe,  has  estimated 
that  as  many  as  87,360  such  pearly  drops  occurred  in 
a  net  of  average  dimensions,  and  120,000  in  a  large  net 
of  fourteen  or  sixteen  inches  diameter ;  and  yet  a  Spider 
will  construct  such  a  net,  if  uninterrupted,  in  less  than 
three-quarters  of  an  hour. 

Scarcely  less  admirable  are  the  ease  and  precision  with 
which  the  little  architect  traverses  her  perpendicular  or 
diagonal  web  of  rope  ;  a  skill  which  leaves  that  of  the 
mariner  who  leaps  from  shroud  to  backstay  in  a  ship's 
rigging  immeasurably  behind.  To  understand  it,  however, 
in  some  measure,  look  at  this  last  joint  of  one  of  the  feet 

*  Mr.  Bichard  Beck  ("  Trans.  Micr.  Soc.,"  ix.  17)  has  ascertained  that 
the  spiral  thread  is,  when  first  spun,  of  uniform  thickness ;  but,  after 
some  exposure,  the  viscid  matter  spontaneously  accumulates  at  most 
regular  distances,  and  forms  itself  into  globules,  which  are  larger  and 
smaller  alternately.  It  is  a  beautiful  example  of  molecular  attraction. 


SPIDERS   AND  MITES.  217 

of  our  well-used  Clubiona.  It  is  a  cylindrical  rod,  ending 
in  a  rounded  point ;  every  part  of  its  surface  is  studded 
with  stiff,  rather  long,  horny  bristles,  which,  springing 
from  the  side,  arch  inward  towards  the  point.  Now  this 
array  of  spines  effectually  prevents  a  false  step,  for  if  any 
part  of  the  leg,  which  is  sufficiently  long,  only  strike  the 
thread,  the  latter  is  certain  to  slip  in  between  the  bristles, 
and  thus  to  catch  the  leg.  But  more  precision  than  this 
is  requisite ;  especially  when  we  observe  with  what  de- 
licacy of  touch  the  hinder  feet  are  often  used  to  guide  the 
thread  as  it  issues  from  the  spinnerets ;  and  particularly 
with  what  lightning-like  rapidity  the  larger  net-weavers 
will,  with  the  assistance  of  these  feet,  roll  a  dense  web  of 
silk  around  the  body  of  a  helpless  fly,  swathing  it  up, 
like  an  Egyptian  mummy,  in  many  folds  of  cloth,  in  an 
instant. 

Look,  then,  at  the  extreme  tip  of  the  ultimate  joint. 
Two  stout  hooked  claws  of  dark  horny  texture  are  seen 
proceeding  from  it  side  by  side,  and  a  third  of  smaller 
size,  and  more  delicate  in  appearance,  is  placed  between 
them  and  on  a  lower  level.  The  former  have  their  under 


CLAWS   OP   SPIDER. 


or  concave  surface  set  with  teeth  (eighteen  on  each  in  this 
example),  very  regularly  cut,  like  those  of  a  comb,  which 
are  minute  at  the  commencement  of  the  series  near  the 
base  of  the  claw,  and  gradually  increase  in  length  to  the 
tip.  These  are  doubtless  sensible  organs  of  touch,  feeling 
and  catching  the  thread;  and  they,  moreover,  act  as 
combs,  cleansing  their  limbs,  and  probably  their  webs, 


218  EVENINGS  AT   THE  MICROSCOPE. 

from  the  particles  of  dust  and  other  extraneous  matter 
which  are  continually  cleaving  to  them. 

There  are  Spiders  in  the  sea  also.  I  can  show  you  one 
which  is  sufficiently  common  on  the  southern  shores, 
sprawling  and  crawling  sluggishly  among  the  filamentous 
sea-weeds  and  branching  flexible  zoophytes.  Here  it  is, 
Nymphon  by  name. 

Its  most  prominent  characteristic  is  the  exceeding  slen- 
derness  of  all  its  parts,  but  especially  its  eight  legs,  which 
are  greatly  lengthened,  each  comprising  eight  joints,  and 
no  thicker  than  the  finest  thread.  On  the  other  hand, 
the  body  is  reduced  to  a  minimum ;  the  abdomen,  which 
in  the  Spiders  and  Harvestmen  of  the  land  is  so  bulky  as 
to  constitute  the  chief  volume  of  the  animal,  is  here  so 
minute  that  you  will  have  some  difficulty  in  finding  it 
at  all ;  it  is,  in  fact,  that  tiny  atom  of  a  point  that  pro- 
jects between  the  hindmost  pair  of  limbs.  The  thorax, 
indeed,  is  a  little  more  developed;  but  even  this  has 
scarcely  any  appreciable  breadth  or  thickness,  being 
^scarcely  more  than  the  extended  line  formed  by  the  suc- 
cessive points  of  origin  of  the  limbs. 

The  head,  however,  is  distinct  and  well  furnished.  It  is 
crowned  with  a  short  column,  much  as  in  the  Harvestman, 
on  the  summit  of  which  are  placed  four  black  eyes,  set  in 
square  ;  these,  under  the  magnifying  power  which  we  are 
applying  to  them,  gleam  like  diamonds,  the  light  being 
highly  refracted  through  them.  It  is  the  high  refractive 
power  of  these  eyes,  as  of  those  which  we  have  lately 
been  examining,  which  makes  them  appear  black  ;  for, 
as  I  have  explained,  they  are  really  transparent  lenses, 
covered  with  polished  corneae,  and  furnished  with  the  other 
essential  requisite  for  the  transmission  of  the  rays  of 
light  to  the  optic  nerve,  or,  as  in  this  case,  direct  to  the 
brain. 

In  front,  you  see,  the  head  projects  into  a  stout  oval  or 
cylindrical  proboscis,  terminating  in  a  small  mouth  and 


SPIDERS   AND    MITES.  219 

stout  jaws,  and  furnished  at  the  sides  with  a  pair  of  spine- 
like  palpi,  and  a  pair  of  pincer-claws  (modified  antennae) 
somewhat  resembling  the  nippers  of  a  Crab  or  Lobster. 

Such  is  the  outward  form  of  this  tiny  speck,  the  whole 
body  of  which  scarcely  equals  in  dimensions  a  quarter  of 
an  inch  of  sewing  cotton.  And  now  I  will  beg  your  at- 
tention to  the  singular  manner  in  which  digestion  is  carried 
on  in  this  atom.  You  will  discern  it  plainly  enough 
through  the  brown  but  translucent  skin.  If  you  look 
carefully  at  either  of  the  long,  many-jointed  legs,  you  will 
see  that  it  is  permeated  by  a  central  vessel,  the  walls  of 
which  contract  periodically  with  a  pulsation  closely  resem- 
bling that  of  a  heart,  by  which  granules  or  pellucid  cor- 
puscles, floating  in  a  clear  fluid,  are  forced  forward. 
There  is  no  uniformity  in  the  direction  of  the  pulsatory 
waves ;  sometimes,  as  in  the  limb  we  are  watching,  they 
proceed  from  the  body  towards  the  extremity;  but,  in 
some  of  the  others,  we  shall  probably  find,  even  at  the 
same  moment,  that  the  waves  have  an  opposite  course ; 
and  this  contrariety  may  occur  in  two  contiguous  limbs  on 
the  same  side  of  the  animal.  By  continuing  our  obser- 
vation for  some  minutes,  we  shall  find  also  that  its  force 
is  varying  and  uncertain  ;  strong  and  regular  at  one  time, 
weak  and  irregular  at  another,  and  sometimes  even  quite 
intermitted,  or,  at  least,  quite  imperceptible. 

By  selecting  a  limb  in  which  the  movements  are  strong, 
you  may  trace  the  vessel  to  its  termination  in  a  blind  sac 
in  the  last  joint  but  one  of  the  limb  ;  and  then  follow  it 
up  to  its  junction  with  a  great  vessel  which  runs  longi- 
tudinally through  the  trunk,  of  which  all  the  vessels  that 
permeate  the  limbs  are  branches,  and  whence  the  circu- 
lating globules  all  proceed.  This  great  vessel  is  the 
stomach;  and  this  circulation  is  the  provision  for  dis- 
persing the  nutritive  properties  of  the  food  to  all  parts 
of  the  system.  There  is  in  these  humble  and  simply- 
organised  animals  no  proper  blood,  or,  at  least,  none 


220  EVENINGS   AT    THE    MICROSCOPE. 

included  in  a  system  of  arteries  and  veins ;  but  the  pro- 
ducts of  digestion  are  carried  to  the  most  distant  parts  of 
the  body  through  this  extraordinary  development  of  the 
stomach  or  intestine  (both  in  one),  and  through  this  series 
of  blind  canals,  by  means  of  their  own  irregular  con- 
tractions, aided  by  the  muscular  movements  of  the  body 
and  limbs. 

You  would  scarcely  forgive  me  if  I  took  no  opportunity 
of  showing  you  the  Cheese-mite,  that  first  object  of  wonder 
to  every  child  that  looks  through  a  magnifying-glass.  And 
it  could  not  be  more  suitably  introduced  than  in  con- 
nexion with  its  cousins,  the  Spiders  and  Harvestmen. 
Well,  fortunately,  we  need  not  search  far  for  specimens ; 
for  here,  in  the  cavity  of  this  almost  defunct  skeleton  of  a 
cheese,  we  can  find  as  many  millions  as  you  can  reasonably 
desire  to  select  from.  Here  is  a  fat  one  ;  we  '11  take  him. 

You  can  see  with  a  pocket  lens  that  it  has  a  plump, 
polished,  oval  body,  of  a  pellucid  white  hue,  and  eight 
short  red  legs  ;  but  for  more  than  this  we  must  go  to  the 
tube.  Look  at  him  now,  as  he  lies  on  his  back,  helplessly 
sprawling  and  throwing  his  feeble  legs  about,  in  the 
live-box. 

His  oval  body  is  divided  by  a  transverse  furrow  into 
thorax  and  abdomen,  like  a  Beetle's  ;  and  there  is  another 
division  between  the  head  and  thorax,  wherein  it  differs 
from  the  Spider's.  The  first  two  pairs  of  legs  are  separ- 
ated by  an  interval  from  the  last  two  pairs  ;  they  are  all  of 
a  translucent  pale  red  hue,  as  is  also  the  head  :  each  con- 
sists of  seven  short  joints,  the  last  of  which  has  a  sort  of 
heart-shaped  pad,  something  like  a  horse's  hoof,  and  a 
single  hooked  claw,  which  works  against  its  sole. 

The  structure  of  the  head  cannot  be  seen  satisfactorily 
otherwise  than  by  crushing  the  Mite  in  the  compressorium  ; 
a  process  which,  when  we  remember  how  many  thousands 
we  crush  down  in  our  oral  compressorium  every  time  we 
eat  ripe  cheese,  needs  not  excite  much  compunction.  We 


SPIDERS    AND    MITES. 


221 


must  put  a  drop  of  water  between  the  plates,  in  order  to 
wash  away  the  opaque  granules  which  will  escape  from  the 
bodies  of  the  animals ;  after  which  the  skin,  and  all  the 
solid  parts,  will  be  left  beautifully  clear  and  distinct. 
Moreover,  by  putting  half-a-dozen  specimens  in  at  once 
we  shall  secure  them  pressed  in  various  aspects,  and  be 
pretty  sure  of  some  perfectly  flat  and  symmetrical. 

I  have  one  under  such  conditions ;  the  parts  of  the 
mouth  nicely  expanded,  and  the  whole  well  displayed. 
Now  for  a  high  power ;  for,  to  discern  this  properly,  we 
cannot  do  with  less  than  600  diameters. 


HEAD  OF   CHEESE-KITE. 


Viewed  from  beneath,  we  see  a  broad  labium,  nearly 
square,  divided  at  the  tip  into  two  blunt  points,  with  a 
sharp  notch  between  them.  The  two  lateral  edges  are,  as 
it  were,  buttressed  by  the  pair  of  palpi,  which  are  thick, 
and  consist  of  four  joints  each ;  these  are  distinguished 
by  the  bristles  at  each  joint,  though  the  whole  are  united ; 
soldered,  as  it  were,  to  the  sides  of  the  lip. 

The  upper  portion  of  the  mouth  is  formed  by  two  stout 
mandibles,  which  are  jointed  to  the  front  of  the  head,  and 


222  EVENINGS   AT    THE   MICROSCOPE. 

can  be  either  widely  expanded,  or  brought  together  so  as 
to  form  a  covering  to  the  labium.  They  are  pincer-form, 
like  the  claws  of  a  crab,  the  two  fingers  being  strongly 
toothed  on  their  opposing  surfaces.  They  thus  form 
effective  prehensile  instruments.  These  mandibles  can  be 
advanced  separately  or  together,  and  the  whole  head  can 
be  elevated  or  depressed. 

In  the  water  of  ponds  we  may  frequently  see,  playing 
among  the  sub-aquatic  vegetation,  bright- coloured  Mites  ; 
sometimes  rich  velvety  green,  sometimes  purple,  but  more 
commonly  brilliant  scarlet ;  often  curiously  marked  with 
sinuous  patterns  or  spots  of  black.  They  swim  rapidly 
and  evenly  by  means  of  rapid  rowings  with  their  legs, 
which  are  thickly  fringed  with  long  hairs.  I  have  one 
here,  which  seems  to  be  the  Hydrachna  histrionica.  It  is 
a  little,  flat,  circular,  cushion  or  cake-like  creature,  scarlet, 
with  four  clouds  of  black  on  its  back,  about  one-sixth  of 
an  inch  in  diameter.  You  may  notice  the  effective  oars 
which  the  legs  form  by  means  of  their  thick  fringe  of  hair, 
and  in  particular  the  power  which  the  hind  pair  possess  by 
reason  of  the  enormously  dilated  hip-joint,  affording  space 
for  broad  and  powerful  muscles. 

The  structure  of  the  mouth  differs  greatly  from  the 
same  parts  in  the  Cheese-mite.  The  palpi  here  are  long 
and  perfectly  free  throughout ;  the  fourth  joint  is  long 
and  slender,  and  is  curiously  hollowed  at  the  end  to  re- 
ceive the  terminal  joint,  which  forms  a  short  claw,  and 
which  falls  down  upon  the  former.  The  mandibles,  too, 
are  not  pincers,  but  consist  each  of  a  thick  joint,  cut  off 
obliquely  behind,  like  the  nib  of  a  pen,  while  the  other 
extremity  is  blunt  and  broad,  and  bears  a  strong  curved 
claw  ;  the  lip  is  oval,  and  cleft  in  the  middle,  and  is  wedged 
in  between  the  bases  of  the  first  pair  of  legs. 


WHEEL-BEARERS.  228 


CHAPTER  XIV. 

WHEEL-BE  ABEBS . 

I  MUST  now  introduce  to  you  a  class  of  animals  peculiarly 
microscopic,  since  without  our  marvel- showing  instrument 
they  are  wholly  beyond  the  sphere  of  human  cognisance. 
Yet  they  have  been  ever  since  its  invention  favourite 
objects  with  the  microscopist ;  and  I  am  free  to  confess 
that,  among  all  the  classes  of  animated  beings,  this  of  the 
Rotifera  *  has  been  my  own  special  delight.  Their  numer- 
ous and  varied  forms,  often  of  remarkable  symmetry  and 
elegance,  their  swiftly-revolving  wheels,  their  vigorous  and 
sprightly  motions,  their  curious  habits  and  instincts,  their 
complete  organisation,  and  the  ease  and  correctness  with 
which  this  is  discerned  through  their  tissues,  which  have 
the  transparent  brilliance  of  the  purest  crystal, — all  com- 
bine to  impart  a  charm  to  the  Wheel-bearers,  which  makes 
the  observer  hail  their  appearance  in  his  drops  of  water 
with  pleasure,  and  linger  over  them  with  unwearied  de- 
light. 

The  peculiarity  which  specially  characterises  them  is 
the  presence  of  certain  organs  called  cilia,  and  their 
arrangement  in  such  a  manner  that  their  motion  gives  to 
the  observer  the  impression  that  two  toothed  wheels  are 
placed  on  the  front  of  the  animal,  which  are  in  rapid  re- 
volution on  their  axes.  This  was  believed  to  be  the  real 
fact  by  the  earlier  microscopists,  though  they  were  utterly 
unable  to  conceive  how  such  a  movement  could  consist 
with  parts  maintaining  an  organic  connexion  between 

*  From  the  Latin  rota,  a  wheel,  and/ero,  I  bear. 


224  EVENINGS    AT    THE    MICROSCOPE. 

themselves.  It  is,  however,  an  optical  illusion,  depending 
on  the  nature  of  ciliary  movement,  which  therefore  I  must 
first  endeavour  to  explain  to  you. 

Cilia  are  organs  which  play  a  very  important  part  as 
instruments  of  locomotion,  as  well  as  of  other  functions, 
in  all  the  lower  forms  of  animals,  and  in  the  early  stages 
of  some  of  the  higher  forms.  They  are  also  found  cha- 
racterising the  lowest  form  of  vegetable  life,  giving  to  them 
the  means  of  spontaneous  locomotion,  which  renders  them 
liable  to  be  mistaken  for  animals.  They  consist  of  pro- 
longations of  the  fleshy  tissue  into  long  and  very  delicate 
hairs,  which  are  endowed  with  a  special  faculty  of  motion. 
This  consists  of  a  bending  down  in  a  given  direction  to  a 
certain  extent  of  flexure,  followed  by  a  rapid  resuming  of 
the  perpendicular ;  which  is,  however,  immediately  suc- 
ceeded by  like  bendings  and  straightenings  in  alternate 
gradation.  The  simplest  condition  of  this  movement  is 
that  in  which  a  single  cilium  only  exists,  by  whose  succes- 
sive lash-like  beats  upon  the  surrounding  water  the  ani- 
mal is  rowed  along  like  a  boat  through  the  sea.  But  far 
more  commonly  cilia  are  arranged  in  rows,  or  in  many 
series  of  rows,  in  which  ease  the  bending  and  straightening 
of  the  individual  cilia  do  not  occur  otherwise  than  in  strict 
and  orderly  relation  to  each  other.  For  instance,  one 
cilium  in  a  given  row  begins  to  bend,  the  one  next  to  it 
then  begins,  then  the  third,  then  the  fourth,  and  so  on,  all 
precisely  in  the  same  direction,  all  in  precisely  the  same 
time,  all  with  precisely  the  same  force,  and  all  to  precisely 
the  same  extent.  It  follows,  that  before  the  first  has  com- 
pleted its  beat  and  resumed  the  erect  position,  three  or 
four  others  are  in  various  degrees  of  flexion,  regularly 
graduated ;  and  that  if  the  eye  could  look  laterally  at  such 
a  row  of  cilia  suddenly  arrested  and  fixed  as  they  were, 
we  should  see  their  tips  tracing  a  wavy  line  instead  of  a 
straight  one.  Moreover,  since  the  bending  of  any  cilium 
brings  its  tip  nearer  to  its  successor  than  it  was  before, 


WHEEL-BEAKERS.  225 

and  this  approximation  increases  the  farther  the  flexure 
proceeds,  it  follows  that  at  the  bottom  of  each  wave  the 
tips  of  the  cilia  overlap  their  successors,  while  the  spaces 
perpendicularly  above  their  bases  are  left  more  open  by 
the  removal  of  their  points. 

Hence,  in  microscopical  observation  of  ciliated  animals, 
though  the  individual  cilia  are  too  minute  to  be  discerned 
while  still,  we  can  readily  discern  the  increased  density 
(and  therefore  opacity)  of  the  bottom  of  a  wave,  contrasted 
•with  the  increased  openness  (and  therefore  clearness)  of 
the  summit.  So  that  the  optical  effect  is  that  of  an  alter- 
nate succession  of  dark  and  light  spots  blending  into  each 
other. 

But  as  no  cilium  in  the  series  is  for  two  successive 
moments  in  the  same  degree  of  flexure,  and  as  both  it  and 
all  its  predecessors  and  successors  are  ever  urging  on  their 
perfectly  timed  and  regulated  course,  the  waves  are  never 
fixed,  but  always  gliding  on  with  a  swift  but  beautifully 
even  rapidity.  And  as  it  is  with  the  waves,  so  it  is  with 
their  optical  effect  upon  the  eye  ;  the  black  and  white 
spots,  or  rather  the  black  spots  with  blank  intervals, 
appear  to  be  constantly  chasing  each  other  in  ceaseless 
race. 

You  are  then  prepared  to  take  a  peep  at  this  beautiful 
Brachionus  pala.  A  cup  of  elegant  form,  swelling  at  the 
sides  and  narrowing  a  little  at  the  mouth,  has  one  side  of 
its  rim  furnished  with  four  spines,  the  middle  pair  of 
which  are  very  slender,  sharp,  and  needle-like;  the  other 
side  of  the  rim  is  undulated,  but  not  toothed.  The  bottom 
of  the  cup  terminates  in  two  broad,  blunted  points — when 
seen  directly  in  front;  but  a  lateral  view  considerably 
modifies  the  whole  form.  Then  you  see  that  the  back  of 
the  cup  is  much  more  swollen,  the  belly-edge  being  nearly 
straight,  and  that  this  latter  descends  much  lower  than 
the  dorsal  line,  the  bottom  being  as  it  were  cut  away 
obliquely  and  slightly  hollowed.  Between  the  two  bottom 

Q 


226  EVENINGS    AT    THE    MICROSCOPE. 

points,  there  is  a  round  opening,  for  an  object  which  we 
shall  see  presently.  Such  is  the  shell,  or  lorica,  as  it  is 
technically  called,  which  is  of  a  rather  stiff,  elastic  consist- 
ence, of  a  horny  (chitinous)  texture,  and  of  the  most 
glassy  transparency,  permitting  us  to  trace  every  vessel, 
every  organ,  and  every  function  of  the  animal  within  the 
shell  with  perfect  distinctness.  The  little  creature  is  of 
unwonted  dimensions  in  its  class,  for  it  is  one  thirty-sixth 
of  an  inch  in  length.  Hence,  to  the  unassisted  eye,  it  is 
just  visible  as  a  white  speck  moving  in  the  water,  while  a 
pocket  lens  reveals  its  beautiful  form. 

Within  this  translucent  shell  you  see  a  confused  mass 
of  moving  viscera,  a  multitude  of  irregular  sacs  and  bands, 
lying  over  each  other,  whose  crowding,  changing,  and 
vanishing  lines  distract  the  attention,  and  prevent  you 
from  making  out  anything  definitely.  But  a  waved  out- 
line of  limpid  flesh  is  protruding  from  the  rim  of  the  shell ; 
and  now,  having  reached  beyond  the  level  of  the  spine- 
points,  it  rapidly  unfolds  into  three  broad,  flattish  lobes  ; 
and  in  an  instant  each  of  the  two  lateral  ones  is  crowned 
by  a  wheel  of  dark  points  in  rapid  horizontal  revolution. 
Is  not  this  a  charming  sight  ?  Round  and  round  go  the 
wheels,  forming  two  perfect  crowns,  which  rotate  with 
uninterrupted  and  unceasing  course,  smooth  and  regular, 
which  we  can  compare  with  nothing  else  than  the  crown- 
wheel of  a  watch,  if  allowed  to  run  down. 

Now  these  are  examples  of  ciliary  action.  Though  at 
first  it  is  almost  impossible  to  persuade  oneself  that  there 
is  not  an  actual  rotation  of  parts,  yet  this  is  only  an  illu- 
sion, as  I  have  already  explained.  The  waves  alone  move, 
the  cilia  themselves  retaining  their  position  unchanged, 
except  that  they  alternately  bend  and  erect  themselves. 
It  may  assist  your  idea  of  this  motion  to  advert  to  a  field 
of  corn  over  which  a  smart  breeze  is  blowing.  You  see 
that  waves  chase  each  other  across  the  field ;  but  your 
reason,  indeed  your  observation,  tells  you,  that  this  appear- 


WHEEL-BEAKEBS.  227 

ance  is  produced  entirely  by  the  alternate  bending  and 
rising  of  the  ears  of  corn,  which  are  of  course  stationary. 

The  beauty  and  wonderfulness  of  these  ciliary  wheels 
are  so  striking,  especially  when  one  sees  them  for  the  first 
time,  that  for  awhile  we  see  nothing  else  ;  we  cannot  take 
our  eye  off  from  them.  But  when  you  have  a  little  satis- 
fied your  sense  of  seeing,  you  may  examine  other  points 
of  interest  in  this  charming  little  animal. 

The  cilia  are  remarkably  stout  and  long  in  this  genus, 
but  on  the  middle  lobe  of  the  front  there  are  other  pro- 
cesses of  the  same  character ;  but  still  stouter.  These 
too  are  not  properly  vibratile,  at  least  they  do  not  make 
circular  wheels  :  ordinarily,  they  project  like  stiff  erect 
bristles,  or  converge  towards  each  other. 

Between  the  two  middle  spines  the  shell  is  cut  into  a 
d^ep  notch,  out  of  which  protrudes,  when  the  wheels  are 
expanded,  a  curious  little  organ,  consisting  of  fleshy  tubes, 
the  one  sheathed  in  telescopic  fashion  within  the  other, 
and  bearing  at  its  tip  a  pencil  of  bristles,  which  can  in 
turn  be  sheathed.  This  organ  doubtless  represents  the 
united  antennas  of  insects. 

But,  you  ask,  what  is  that  much  more  conspicuous 
organ  that  is  alternately  thrust  out  and  drawn  back  at  the 
bottom  of  the  shell,  and  that  is  so  nimbly  whisked  about 
in  all  directions,  looking,  with  its  numberless  transverse 
wrinkles,  and  its  little  fingers  at  the  tip,  so  like  an  ele- 
phant's trunk  in  miniature  ?  This  is  the  creature's  foot ; 
the  only  one  he  has  ;  and  as  I  said  the  little  tubular  tele- 
scope represents  the  two  antennae  fused  into  one,  so  we 
must  consider  that  this  flexible  member  represents  all  the 
six  pairs  of  an  insect's  legs  united,  or  perhaps,  more  scien- 
tifically, one  of  the  pairs,  the  rest  being  obsolete  or  un- 
developed. It  must  not  be  considered  as  a  tail, — not  only 
from  its  function,  which  is  decidedly  that  of  locomotion, 
but  also  from  its  position  on  the  ventral  side  of  the  intes- 
tinal orifice.  It  is  a  curious  organ,  capable  of  great  elong- 
Q2 


228  EVENINGS   AT    THE  MICROSCOPE. 

ation,  or,  at  the  will  of  the  animal,  of  entire  retractation 
within  the  abdomen ;  and  this  in  an  instant :  while,  as 
you  observed,  it  is  flung  about,  and  dashed  from  side  to 
side,  and  bent  hither  and  thither  with  a  sort  of  insane 
energy.  The  means  by  which  these  movements  are  per- 
formed, you  may  easily  discern  in  several  pairs  of  muscu- 
lar bands  which  run  throughout  its  whole  length,  their 
upper  insertions  being  placed  high  up  on  the  interior  of 
the  shell,  where,  during  contraction,  you  may  see  them 
swollen  into  thick  bulbs. 

The  foot  terminates  in  two  short  conical  fingers  or  toes, 
which  can  be  drawn  in  or  extended,  widely  separated  or 
brought  into  contact,  at  pleasure.  By  means  of  these  the 
animal  has  the  power  of  mooring  itself,  even  to  the  smooth 
surface  of  glass  ;  and  that  so  firmly  that  from  them  it  can 
stretch  itself  in  all  directions  by  turns,  now  and  then  shak- 
ing itself  to  and  fro  with  sudden  violence,  as  if  irritated, 
yet  without  letting  go  its  foot-hold. 

While  thus  anchored,  the  action  of  the  ciliary  wheels 
produces  considerable  whirlpools  in  the  surrounding  water, 
as  you  will  see  very  distinctly  when  we  have  recourse  to 
a  curious  but  simple  expedient,  first  invented  by  Gleichen, 
and  since  much  used  by  Ehrenberg,  of  mixing  some 
colouring  matter  with  the  water  in  which  the  animal  is. 
I  take  a  little  carmine  with  a  wetted  hair-pencil,  as  if  I 
were  going  to  colour  a  drawing,  and  allow  a  small  portion 
of  the  pigment  to  diffuse  itself  in  the  water  which  is  in  the 
live-box,  then,  putting  on  the  cover,  I  quickly  replace  the 
whole  on  the  stage,  and  re-find  my  little  Brachion :  and 
now  I  again  submit  it  to  your  observation. 

The  whole  field  is  now  filled  with  scattered  granules  of 
irregular  form  and  size,  of  a  dark  red  hue.  These  are  the 
particles  of  carmine  floating  in  the  water ;  particles  of 
alumina,  that  is  to  say,  stained  with  cochineal.  They  are 
in  motion,  and  their  movement  is  more  energetic  the 
nearer  they  are  to  the  little  animal,  which  is  rotating 


WHEEL-BEARERS.  229 

vigorously  in  the  midst  of  them.  They  describe  two  great 
circles,  concentrical  with  the  two  wheels  of  the  Brachionus, 
and  it  is  easy  to  see  that  their  rotations  are  .the  cause  of 
the  movement.  The  motion  of  the  cilia  communicates 
itself  to  the  surrounding  water,  and  produces  circular  cur- 
rents, into  which  every  floating  atom  within  a  certain  dis- 
tance is  drawn,  and  in  which  it  then  continues  to  whirl 
round  with  a  rapidity  which  increases  as  it  approaches  the 
centre  of  rotation. 

But  the  Brachionus  suddenly  lets  go  its  foot-hold,  and  a 
surprising  change  takes  place.  No  more  currents  are  made 
in  the  water,  but  the  animal  itself  glides  swiftly  away  head 
foremost  with  an  even  course,  revolving  on  its  axis  as  it 
goes.  What  is  the  immediate  cause  of  its  movement  ? 
The  ciliary  action  which  before  produced  vertical  currents. 

In  order  to  explain  this,  let  me  suggest  to  you  a  homely 
comparison.  Suppose  you  see  a  boat  on  a  still  lake,  and 
in  it  a  man  pulling  a  pair  of  oars.  He  pulls  vigorously, 
but  the  boat  does  not  move  an  inch,  and  you  perceive  that 
she  is  fast  moored  ;  a  rope  holds  her  to  a  post  on  the 
bank.  But  does  the  man's  rowing  produce  no  effect  ?  0 
yes  ;  the  successive  strokes  of  the  oars  upon  the  water 
have  communicated  motion  to  the  fluid,  and  a  strong  cur- 
rent is  made  on  each  side  of  the  boat,  in  a  direction  oppo- 
site to  that  in  which  he  strives  to  row  her  forward,  the 
force  of  which  is  felt  to  a  distance  proportionate  to  the 
vigour  and  continuance  of  his  pulling.  The  reason  of  this 
is  that  the  boat  is  fixed,  and  all  the  force  of  the  impact  is 
spent  on  the  water. 

But  now  another  man  approaches  the  post,  and  unties 
the  rope.  Instantly  the  boat  glides  ahead,  and  continues 
to  do  so,  urged  by  the  repeated  strokes  of  the  oars,  whose 
eflect  on  the  water  in  making  currents  is  now  slight  and 
imperceptible.  The  reason  of  this  is  that  the  water  is  now 
a  fixed,  body  (or  nearly  such),  and  the  force  of  the  impact 
is  mainly  spent  on  the  movable  boat. 


230  EVENINGS   AT    THE    MICROSCOPE. 

The  Brachionus  is  the  boat,  its  cilia  are  the  oars,  and 
its  foot  is  the  rope.  As  long  as  this  last  maintains  its 
hold,  the  whole  force  of  the  ciliary  stroke  is  spent  on  the 
water,  and  currents  are  the  result;  but  as  soon  as  this 
hold  is  broken,  the  force  acts  on  the  animal  (=z  boat), 
which  is  thus  rowed  rapidly  forwards. 

The  use  of  the  cilia  in  this  latter  case  is  obvious.  They 
enable  the  little  animal  to  rove  about  at  its  wayward  will ; 
and  doubtless  motion  is  as  pleasant  and  necessary  to  it  as 
to  the  fish  in  the  sea,  or  to  the  bird  in  the  air.  But  what 
is  the  object  of  their  vigorous  rotation,  when  the  animal 
chooses  to  maintain  a  firm  hold  with  its  foot  ?  What  is 
the  use  of  rowing  a  boat,  if  you  do  not  choose  to  let  go 
the  painter  ? 

To  solve  this  enigma,  let  us  search  up  our  little  Brachion 
once  more ;  he  will  not  roam  long  before  he  settles  soberly 
again.  Yes,  here  I  have  him  moored.  Now,  mark  care- 
fully the  vortices,  or  whirlpools,  which  are  so  vigorously 
circling  around  the  animal's  front,  and  you  will  perceive 
that  the  movement  is  not  a  strictly  circular  one,  but  that 
each  whirlpool  has  an  outlet  close  to  the  cilia ;  for  the 
accumulated  and  condensed  particles  of  pigment,  after  many 
rotations,  pass  off  in  an  united  stream  between  the  two 
crowns,  and  go  away  horizontally  in  a  line  from  the  ven- 
tral side  of  the  front.  That  is  to  say,  each  vortex  pours 
off  its  accumulation  at  a  point  on  the  inner  side  of  the 
ciliary  circle,  and  the  two  streams,  uniting,  pass  off  from 
the  lip  of  the  shell,  to  be  drawn  in  again,  however,  by-and- 
by,  when  the  centrifugal  force  is  exhausted. 

Now  this  stream  passes  immediately  over  the  mouth, 
which  is  an  opening  in  the  flesh  of  the  front,  forming  a 
deep  cleft  on  the  ventral  side,  the  lips  of  which,  as  also 
the  whole  interior  of  the  tube,  of  which  it  is  the  orifice, 
are  richly  covered  with  cilia.  A  certain  portion  of  the 
atoms  are  thus  arrested  by  these  cilia,  and  are  hurled  by 
their  vibrations  down  this  gulf.  Yet  not  all,  nor  nearly 


WHEEL-BEABERS.  231 

all ;  for  the  lips  appear  to  possess  the  sense  of  taste,  or  of 
some  modification  of  touch,  which  enables  them  to  refuse  or 
to  receive  the  atoms  presented  to  them,  so  that  only  such 
particles  pass  down  the  throat  as  are  selected  for  food. 
Some  of  the  atoms  of  pigment  are  admitted,  and  one  of 
the  most  pleasing  sights  connected  with  these  animals,  is 
to  watch  the  swallowing  of  coloured  food,  its  reception 
into  the  singular  sunken  mouth,  where  the  great  powerful 
jaws  act  upon  it :  thence  its  dismissal  through  the  gullet, 
where  certain  glands  pour  upon  it  their  secretions,  into 
the  stomach,  where  other  glands,  answering  to  a  liver, 
change  it,  and  thence  into  the  intestine  and  rectum,  until 
its  indigestible  portion  is  discharged  through  the  cloacal 
orifice. 

The  object  of  the  mingling  of  colour  with  the  water  in 
which  these  and  similar  animals  are  held  for  observation, 
was  the  tracing  of  the  phenomena  of  digestion.  And,  in- 
deed, it  renders  the  whole  process  beautifully  distinct ; 
for,  from  the  transparency  of  the  tissues,  the  presence  of 
the  coloured  pellet  is  everywhere  recognisable,  since  it 
retains  its  form  and  hue  under  all  its  changes,  clearly 
revealing  to  us  the  shape,  dimensions,  and  directions  of 
the  various  canals  through  which  it  passes  ;  here  and  there 
diffusing  throughout  the  viscus  in  which  it  is  held  a  beau- 
tiful roseate  hue,  more  or  less  deep,  without,  however, 
losing  its  own  definite  outline. 

Let  me  now  direct  your  attention  to  the  organs  devoted 
to  the  seizing  and  mastication  of  the  food.  And  the  more, 
because  the  form  of  these  organs  in  the  Hotifera  is  quite 
peculiar,  quite  unlike  what  is  found  in  any  other  class  of 
animals ;  though  the  parts  are  essentially  the  same  as 
those  which  we  have  already  seen  entering  into  the  mouth 
in  insects. 

Removing  the  carmine-stained  water,  I  put  into  the 
live-box  a  drop  from  a  vase  very  rich  in  organisms  of 
many  kinds.  Among  these  you  see  very  numerous  the 


232 


EVENINGS    AT    THE    MICROSCOPE. 


mulberry-like  clusters  of  that  beautiful  green  creature, 
Syncrypta  volvox,  which  is  now  pretty  generally  considered 
a  plant,  though  from  its  spontaneous  motion,  swimming 
evenly  along,  revolving  on  its  axis  as  it  goes,  you  would 
be  inclined  to  agree  with  earlier  observers  in  thinking  it 
an  animal.  These  appear  to  be  favourite  morsels  with  the 
Brachion  :  one  has  already  been  devoured,  and  is  quite 
visible  in  the  alimentary  canal,  its  brilliant  green  hue 
shining  out  through  the  translucent  viscera  and  tissues. 

Others  are  approaching, 
and  two  or  three  are  just 
now  drawn  into  the  vor- 
tex of  the  ciliary  current. 
It  is  amusing  to  see  the 
manoeuvres  which  the  Bra- 
chionus  makes  to  take  his 
prey.  I  say  manoeuvres, 
for  there  really  seem  to 
be  perception  and  intelli- 
gence. The  mode  in  which 
it  directs  its  ciliated  flaps 
towards  the  spot  where  a 
Syncrypta  is  whirling,  or 
suddenly  stretches  forward 
to  the  extent  of  the  long 
foot,  as  if  it  would  seize 
the  prey  by  force,  seems 
to  indicate  a  cognizance  of 
its  proximity ;  as  do  also, 
still  more,  the  manner  in 
which  it  depresses  the  lip- 
like  lobes  of  the  rotatory  organ  on  one  side,  when  the 
prey  is  in  the  vortex  on  that  side,  and  the  eager  haste 
with  which  it  shrinks  down  into  its  shell  the  instant  the 
little  mulberry  drops  at  length  into  the  throat. 

But  now  comes  the  tug  of  war ;  the  black,  millstone- 


BRACHIOJOTS. 


WHEEL-BEAREES.  233 

like  jaws  open  wide  and  stretch  forward  to  grasp  the  little 
victim  (which  is  still  distinctly  visible  through  the  trans- 
parent tissues) :  they  touch  the  globular  envelope,  but 
cannot  quite  grasp  it.  The  Brachion  redoubles  its  efforts  ; 
the  jaws  gape  vigorously,  but  can  only  scrape  the  sides  of 
the  little  globe,  which  at  every  touch  slips  away,  the  expanse 
of  the  jaws  being  not  quite  sufficient  to  embrace  it. 

At  last  the  little  animal  becomes  indignant ;  the  jaws 
no  more  endeavour  to  grasp,  but  with  a  very  distinct  and 
sudden  upward  jerk  throw  out  the  prey,  which  until  now 
has  been  retained  and  pressed  downward  by  the  contrac- 
tion of  the  sides  of  the  sensitive  throat.  Strange  to  see, 
the  little  Syncrypta,  after  all  its  imprisonment  and  rough 
handling,  is  no  sooner  free  than  it  whirls  merrily  away, 
revolving  as  it  pursues  its  even  ciliary  course,  just  as  if  no 
interruption  of  its  freedom  had  occurred. 

Meanwhile,  however,  better  success  attends  the  Bra- 
chion's  hunting ;  for  a  smaller  globe  has  sunk  into  the 
throat,  and  passes  with  a  gulp  into  the  mouth,  between 
the  gaping  jaws,  which  instantly  close  upon  it,  and,  working 
vigorously,  bruise  it  down  with  a  hammer-like  action  upon 
a  sort  of  central  table.  After  this  process  has  gone  on 
for  a  few  minutes,  the  green  mass,  less  perfectly  denned 
than  before,  slips  through  a  narrow  postern-gate,  along  a 
short  slender  alley,  into  the  digesting  stomach. 

But  what  sort  of  a  mouth  is  this  ?  It  is  inclosed  within 
the  tissues  of  the  body,  not  very  far  from  its  centre,  so 
that  no  part  of  it  comes  into  contact  with  the  external 
water,  or  even  approaches  any  portion  of  the  superficies  of 
the  body.  It  has  been  usual  to  call  the  great  hemispheric 
bulk  in  which  the  symmetrical  hammers  work  so  vigor- 
ously, a  gizzard ;  but  it  is  a  true  mouth,  and  the  hammers 
are  true  jaws. 

This  form  of  mouth  is  termed  a  mastax ;  it  consists  of  a 
dense  but  transparent  muscular  mass,  forming  three  lobes 
at  its  lower  part,  deeply  cleft  at  the  front  of  its  ventral 


234  EVENINGS   AT    THE    MICROSCOPE. 

side,  where  the  passage,  which  I  have  called  the  throat, 
but  which  is  more  correctly  designated  the  buccal  funnel, 
enters.  Within-  this  muscular  bulb  are  placed  two  bent 
organs  like  hammers,  called  mallei,  and  a  third  central 
table,  called  the  incus.  The  mallei  approach  each  other 
dorsally,  while  the  incus  is  placed  towards  the  ventral 
side,  its  stem  pointing  obliquely  away  from  the  centre. 

Each  malleus  consists  of  two  portions,  united  by  a  free 
but  powerful  hinge-joint.  The  lower  joint  (manubrium) 
is  shaped  somewhat  like  a  shoulder-blade ;  and  the  upper 
joint  (uncus)  *  is  set  on  at  nearly  a  right  angle  to  it,  but  is 
capable  of  considerable  change  of  direction  by  means  of 
its  hinge.  It  consists  of  five  or  six  finger-like  teeth,  con- 
nected by  a  thin  web  of  membrane. 

The  incus  also  consists  of  several  distinct  pieces.  The 
principal  are  two  stout  rami,  resting  on  what  appears, 
when  you  look  at  the  back  or  belly  of  the  animal,  to  be  a 
slender  foot-stalk  (fulcrum).  But  when  you  get  a  lateral 
view,  the  foot-stalk  is  seen  to  be  only  the  edge  of  a  thin 
plate,  to  the  upper  edge  of  which  are  jointed  the  rami,  in 
such  a  manner  that  they  can  open  and  close,  like  the 
blades  of  a  pair  of  shears.  Each  ramus  is  a  thick,  three- 
sided  piece,  with  the  upper  side  hollow,  and  the  inner 
flat,  and  in  contact  with  that  of  its  fellow,  in  a  state  of 
repose.  The  uncus  of  each  malleus  falls  into  the  concavity 
of  its  corresponding  ramus,  and  is  fastened  to  it  by  a  stout 
triangular  muscle,  which  allows  some  freedom  of  motion. 

Many  muscles  are  inserted  into  various  parts  of  these 
organs,  and  into  the  walls  of  the  mastax,  which  impart 
various  and  complex  motions  to  all  the  parts.  Thus,  as 
we  have  seen,  they  are  adapted  to  the  various  functions  of 
mouth-organs,  those  of  grasping,  holding,  bruising,  and 
chewing  food. 

The  mallei  correspond  with  the  mandibles  of  Insects ; 

*  The  uncus  of  the  malleus  must  not  be  confounded  with  the  incus. 


WHEEL-  BE  ARERS. 

and  the  rami  of  the  incus  with  the  maxillae ;  while  the  walls 
of  the  mastax  with  the  two  edges  of  its  orifice  correspond 
with  the  mouth,  with  its  labrum 
and  labium. 

It  is  true  we  are  somewhat 
startled  to  find  a  mouth  placed 
far  down  within  the  cavity  of  the 
breast  ;  but  there  are  other 
forms  in  this  class,  some  of 
which  I  may  be  able  to  show 
you,  where  the  mastax  has  es- 
sentially the  same  structure,  in, 
which  it  is  placed  at  the  front 
margin  of  the  body,  from  which 
the  jaws  can  be  freely  protruded. 

The  difficulty  will  seem  less  if  you  weigh  the  following 
considerations : — 

The  integument  in  the  Rotifer  a  is  very  flexible,  and, 
especially  in  the  frontal  regions,  is  extremely  invertible. 
In  those  genera  in  which  the  mouth  apparatus  can  be 
brought  into  contact  with  the  external  water,  it  is  ordi- 
narily, to  a  greater  or  less  degree,  retracted  within  the 
body,  by  the  inversion  of  the  surrounding  parts  of  the 
exterior,  while,  in  those  genera  in  which  it  is  permanently 
inclosed,  analogy  requires  us  to  consider  the  condition  as 
induced  by  a  similar  inversion,  but  of  permanent  duration. 
If  we  imagine  the  head  of  a  soft-bodied  Insect-larva  re- 
tracted to  a  great  degree  (as  is  done  partially  by  many 
Dipterous  larva?),  the  skin  of  the  thoracic  segments  would 
meet  together  in  front,  around  a  purse-like  opening,  which 
would  be  the  orifice  of  such  a  buccal  funnel  as  exists  in 
most  Rotifera.  In  the  latter,  it  is  the  normal,  or  proper, 
condition;  in  the  former,  it  is  merely  accidental  and 
temporary. 

We  need  not  devote  any  more  minute  consideration  to 
the  digestive  apparatus  in  our  little  Brachion,  but  there 


236  EVENINGS    AT    THE    MICROSCOPE. 

are  some  other  points  in  its  structure  which  are  worth 
noticing.  In  the  central  line  of  the  body,  just  above  the 
mouth,  as  you  see  the  animal  in  a  dorsal  view,  there  is  a 
square  speck  of  a  rich  crimson  hue,  the  edges  of  which, 
when  we  view  it  under  reflected  light,  glitter  and  sparkle 
like  a  precious  stone.  But  when  we  obtain  a  perfectly 
lateral  view,  we  perceive  that  the  situation  of  this  gem-like 
speck  is  considerably  nearer  the  dorsal  side  of  the  shell 
than  the  mouth,  and  that  it  forms  a  wart-shaped  pro- 
minence on  a  large  turbid  mass  which  occupies  the  whole 
front  portion  of  the  animal.  By  comparison  of  this  organ 
with  the  corresponding  parts  in  other  genera,  there  is 
every  reason  to  infer  that  this  turbid  mass  is  an  enormous 
brain,  the  nervous  matter  being  in  a  very  diffuse  condition  ; 
and  that  the  ruby  seated  on  it  is  an  eye,  consisting  of  a 
crystalline  lens,  and  a  layer  of  crimson  pigment  beneath 
it. 

The  oval  bodies  that  you  see  attached  to  the  hinder 
part  of  the  shell  are  eggs.  Most  of  the  females  that  we 
meet  with  carry  one  or  more,  sometimes  to  the  number  of 
six  or  seven.  The  specimen  we  are  examining  had  two  at 
first,  one  on  each  side  the  foot-orifice  ;  but  just  now  a 
a  third  was  excluded, — an  operation  which  occupied  but  an 
instant, — and  this  took  its  place  beside  the  former  two,  so 
that  we  now  see  three.  These  eggs  are  generally  car- 
ried by  the  parent  until  the  young  are  hatched.  The 
oldest  of  these  three  is  nearly  ready  for  hatching,  and 
if  you  watch  awhile  you  will  see  the  birth  of  the  young. 
At  the  first  exclusion,  the  egg,  which  was  seen  some  time 
before  in  the  ovary,  as  a  semi- opaque  mass,  of  well-defined 
but  irregular  shape,  immediately  assumes  a  form  perfectly 
elliptical,  and  its  coat  hardens  into  a  brittle  shell.  This 
is  so  transparent  that  the  whole  process  of  maturation  can 
be  watched  within  the  shell.  The  yelk  is  at  first  a  turbid 
mass,  in  which  are  many  minute  oil-globules.  Soon  it 
divides  into  two  masses,  then  into  four,  then  into  eight, 


WHEEL-BEARERS.  237 

sixteen,  and  so  on,  by  the  successive  cleavage  of  each 
division,  as  fast  as  it  is  made,  till  these  divisions  are  very 
numerous.  Then  we  begin  to  see  spontaneous  movements ; 
the  outline  of  the  young  separates  in  parts  from  the  wall 
of  its  prison ;  folds  are  seen  here  and  there,  and  fitful 
contractions  and  turnings  take  place.  Soon  an  undefined 
spot  of  red  appears,  which  gradually  acquires  depth  of  tint 
and  a  definite  form,  and  we  recognise  the  eye.  Slight 
waves  are  seen  crossing  one  end  of  the  egg  ;  these  become 
more  and  more  vigorous  and  rapid,  and  at  length  we  see 
that  here  is  the  situation  of  the  frontal  cilia.  The  mastax 
appears,  and  the  jaws,  and  soon  the  latter  begin  to  work ; 
though  it  must  be  only  by  way  of  practice,  for  it  is  hard 
to  imagine  what  they  can  yet  find  to  masticate. 

All  these  phenomena  have  successively  appeared  in  the 
egg  we  are  now  watching ;  and  at  this  moment  you  see 
the  crystalline  little  prisoner,  writhing  and  turning  im- 
patiently within  its  prison,  striving  to  burst  forth  into 
liberty. 

Now  a  crack,  like  a  line  of  light,  shoots  round  one  end 
of  the  egg,  and  in  an  instant  the  anterior  third  of  the  shell 
is  forced  off,  and  the  wheels  of  the  infant  Brachion  are 
seen  rotating  as  perfectly  as  if  the  little  creature  had  had 
a  year's  practice.  Away  it  glides,  the  very  image  of  its 
mother,  and  swims  to  some  distance  before  it  casts  anchor, 
beginning  an  independent  life.  At  the  moment  of  the 
escape  of  the  young,  the  pushed- off  lid  of  the  egg  resumes 
its  place,  and  the  egg  appears  nearly  whole  again,  but 
empty  and  perfectly  transparent,  with  no  evidence  of  its 
fracture  except  a  slight  interruption  of  its  outline,  and  a 
very  faint  line  running  across. 

This  is  a  female  young  :  the  male  is  totally  unlike  the 
female,  and  is  very  much  smaller.  We  can  always  tell 
whether  an  egg  is  going  to  produce  male  or  female  young, 
by  the  great  difference  in  its  size,  the  female  being  more 
than  twice  the  bulk  of  the  male  egg.  All  of  one  brood 


238  EVENINGS   AT    THE    MICROSCOPE. 

are  of  the  same  sex  ;  we  never  see  a  Brachiomts  with  male 
and  female  eggs  at  the  same  time.  What  is  very  strange, 
is,  that  the  male  has  no  shell,  no  spines,  no  mouth,  no 
jaws,  no  stomach,  no  intestines ;  no  ciliary  wheels ;  its 
cilia,  which  are  very  long  and  powerful,  being  arranged  in 
one  circle  round  the  whole  front.  Its  movements  are  ex- 
ceedingly fleet. 

Perhaps  you  are  tired  of  Brachionus,  and  are  ready  to 
cry  out,  "Ohe!  jam  satis!"*  Well,  then,  I  will  turn 
him  off,  and  show  you  another  elegant  little  creature,  the 
Whiptail  (Mastigocei'ca  carinata).  I  have  here  in  a  bottle 
some  stalks  of  the  Water- Horsetail  (Char a  vulgaris),  which 
I  obtained  from  a  pond  a  few  weeks  ago.  These  I  examine 
in  this  way.  Taking  hold  of  the  Cham  with  a  pair  of 
pliers,  I  pull  it  partially  out  of  the  water,  and  allowing  it 
to  rest  on  the  neck  of  the  bottle,  I  cut  off  with  a  pair  of 
scissors,  or  with  a  penknife  on  my  nail,  about  one-fourth 
of  an  inch  of  the  tips  of  three  or  four  leaves,  which  adhere 
together  by  their  wetness.  These  tips  I  place  in  the  live- 
box,  with  a  drop  of  water,  and  having  separated  them  with 
a  needle,  I  put  on  the  cover,  and  examine  them  with  a 
triple  pocket  lens  ;  holding  up  the  box  perpendicularly, 
not  opposite  the  light,  but  obliquely,  so  that  the  field  is 
dark ;  but  the  light  reflected  and  refracted  by  the  ani- 
malcules shows  them  out  beautifully  white  and  distinct, 
even  the  minute  ones.  The  forms  and  some  characters  of 
the  middling  and  larger  can  be  quite  discerned  thus  ;  for 
example,  the  slender  tail  of  the  one  I  am  now  going  to 
show  you,  I  can  thus  see.  The  position  of  any  particular 
individual  to  be  examined  being  thus  marked,  it  is  readily 
put  under  the  object-glass  of  the  microscope.  I  have  found 
these  leaves  very  productive  of  the  more  stationary  ani- 
malcules, the  Rotifer  a  especially. 

It  was  in  this  way  I  this  morning  found  the  pretty  and 
delicate  little  Whiptail,  which  I  am  going  to  make  the 
*  "  0  dear !  quite  enough  of  this ! " 


WHEEL-BEAREBS.  239 

subject  of  our  evening's  study.  It  is  inclosed  in  a  glassy 
shell  (lorica)  of  a  long  oval  form,  from  which  rises  on  the 
front  half  of  the  back  a  thin  ridge,  which  in  the  middle 
has  a  height  nearly  equal  to  half  the  diameter  of  the  body, 
but  tapers  off  at  each  end.  Its  base  is  corrugated  with 
wrinkles.  This  is  not  set  on  symmetrically,  but  leans  over 
considerably  to  the  right  side.  Its  basal  portion  is  hollow, 
and  is  continuous  with  the  general  cavity  of  the  shell,  for 
we  sometimes  see  portions  of  the  viscera  in  its  interior. 


The  head  of  the  animal  is  rounded,  and  divided  into 
several  blunt  eminences  or  lobes,  which  are  set  with  cilia  ; 
these  rotate  constantly,  but  irregularly  and  feebly,  and  do 
not  make  manifest  wheels,  as  Brachionus  does.  A  small 
antenna  projects  from  the  back  of  the  head,  capable  of 
being  erected  or  inclined.  A  long  brain  descends  along 
the  base  of  the  ridge,  carrying  a  bright  and  rather  large 
crimson  eye  set  like  a  wart  on  its  interior  angle. 

Instead  of  the  flexible  and  contractile  foot  of  Brachionus, 
the  Whiptail  has  a  single  horny  spine  of  great  slenderness, 
and  exceeding  in  length  the  whole  body.  This  spine  pro- 
bably represents  not  the  foot,  but  one  of  the  toes  at  the 
end  of  the  foot.  For  it  is  attached  to  a  very  short  foot,  in 
the  midst  of  two  or  three  bract-like  spines,  one  of  which, 
longer  than  the  rest,  and  distinctly  movable,  probably 
represents  the  other  toe  undeveloped.  The  long  spine  is 
set  on  by  a  proper  joint,  a  globose  bulb  being  inserted 
into  a  socket,  which  allows  it  free  motion  in  all  directions 
except  backward.  The  socket  itself  is  contained  in  a 
second  joint,  the  basal  part  of  which  is  inserted  at  some 


240  EVENINGS   AT    THE    MICROSCOPE. 

distance  within  the  aperture  of  the  lorica.  This  articula- 
tion is  formed  by  an  infolding  of  the  skin,  but  is  perma- 
nent in  its  position. 

The  most  remarkable  circumstance  connected  with  this 
elegant  little  animal  is  the  unusual  form  of  the  dental 
apparatus,  which  differs  so  immensely  from  that  of  Bra- 
chionus,  that  we  should  never  recognise  it  as  consisting  of 
the  same  organs,  if  we  had  not  numerous  intermediate  links, 
which  by  insensible  gradations  connect  the  two  remote 
forms. 

The  mastax  is  a  somewhat  slender  sac,  much  produced 
in  length,  and  with  the  component  lobes  greatly  and  irre- 
gularly developed.  The  incus  has  a  fulcrum  of  great 
length  and  slenderness,  a  straight  rod  with  a  dilated  foot. 
The  rami  are  small,  and  pincer- shaped,  but  with  the 
angles  greatly  produced.  The  mallei  have  long,  slender, 
incurved  manubria  and  simple  unci. 

But  the  remarkable  circumstance  is  the  unsymmetrical 
character  of  the  apparatus.  The  left  side  is  much  more 
developed  than  the  right.  The  left  angle  of  the  incus 
descends  to  a  greater  distance  than  the  right ;  and  its 
extremity  is  spread  out  into  a  surface  with  several  irre- 
gular points,  to  which  muscular  threads  are  attached.  The 
ramus  also  of  the  same  side  is  larger  than  its  fellow ;  so 
with  the  mallei.  The  manubrium  of  the  right  is  compara- 
tively short,  very  slender,  and  of  uniform  thickness  ;  with 
a  long,  slender,  rod-like  uncus,  doubly  bent  in  the  middle. 
The  left  is  much  longer,  irregularly  swollen,  clubbed  at  the 
articulation,  and  bearing  a  thick,  curved,  knotted  uncus, 
which  terminates  at  a  point  not  precisely  opposite  the  tip 
of  its  fellow.  These  circumstances,  combined  with  the 
unsymmetrical  character  of  the  dorsal  ridge,  of  the  foot- 
spine,  and  of  some  other  organs,  render  this  genus  a 
highly  curious  one  to  the  naturalist. 

The  little  Whiptail  is  as  lively  in  its  motions  as  it  is 
elegant  in  its  form.  When  swimming,  it  glides  with  con- 


WHEEL-BEARERS.  241 

siderable  swiftness  through  the  water,  turning  frequently 
on  its  course,  and  often  partially  revolving  on  its  long  axis. 
When  inclosed,  as  is  often  the  case,  by  two  fragments  of 
the  filamentous  Chara,  it  travels  along  the  sides  of  its  in- 
closure,  nibbling,  as  it  goes,  the  flocculent  and  sedimen- 
tary deposits  on  the  surfaces  of  the  leaves.  The  long 
spine-foot  is  commonly  carried  inertly  after  it ;  when  the 
animal  suddenly  turns,  of  course  the  tail  is  bent  at  the 
basal  joint,  but  it  is  not  habitually  whisked  about,  as  is 
the  tail  of  Brachionbs,  nor  is  it  so  much  used  as  a  support 
or  turning  point.  The  animal  has  the  power  of  so  using 
it,  however,  and  of  adhering  with  considerable  force  to  the 
glass  of  the  box,  or  the  side  of  a  phial  by  its  point. 

We  have  hitherto  looked  at  our  Eotifera  by  transmitted 
light,  and  their  crystalline  transparency  renders  them  beau- 
tiful objects  when  thus  exhibited.  But  we  will  now  look 
at  the  Whiptail  by  the  direct  light  of  the  sun  upon  it, 
condensed,  but  not  to  a  burning  point,  by  the  bull's-eye 
lens. 

It  now  possesses  a  peculiar  beauty  of  another  character. 
The  body  generally  is  colourless  as  a  vase  of  glass,  but 
reflects  the  rays  brightly  from  its  polished  surface.  An 
advancing  egg  in  the  ovary  is  opaque  white,  as  is  the  front 
part  of  the  mastax ;  the  stomach  and  intestine  filled  with 
vegetable  matter  are  of  a  yellow  green ;  the  rotating  head 
appears  of  a  pale  blue,  and  the  eye  shines  out  as  a  speck 
of  opaque  vermilion. 

With  the  dipping-tube  I  will  now  take  up  a  drop  of 
water  from  the  bottom  of  the  CA«ra-jar,  allowing  a  little  of 
the  loose  sediment  to  flow  in  also.  This  is  a  random  cast ; 
we  know  not  what  we  may  get,  though  we  are  pretty  sure 
to  catch  something.  Now  then  for  the  examination.  Ha  ! 
here  is  the  curious  Skeleton  Wheel-bearer,  Dinocharis 
pocillum  ; — nay,  several  of  them. 

This  genus  is  remarkable  for  possessing  true  joints  in 
the  foot ;  not  merely  telescopic  inversions  of  the  skin,  but 


242  EVENINGS    AT    THE    MICROSCOPE. 

permanent  joints  with  swollen  condyles,  or  rounded  heads, 
resembling  those  of  the  antennae  of  a  beetle.  Hence  the 
Skeleton  has  great  freedom  and  precision  of  motion  ;  using 
the  tips  of  the  long  toes  as  a  fixed  point,  it  throws  its 
body  hither  and  thither  to  a  great  distance,  with  remark- 
able agility.  These  joints  admit  of  forward  and  lateral 
flexure,  but  you  never  see  the  body  brought  backward 
beyond  a  perpendicular  position,  the  swelling  of  the  ter- 
minal portion  of  each  articulation  precluding  further  mo- 
tion in  that  direction ;  just  as  the  joitfts  of  our  knees  and 
elbows  permit  bending  in  one  direction,  but  not  in  the 
other. 

This  is  another  indication  that  these  divisions  are  true 
joints  ;  and  I  direct  your  attention  to  the  point,  because 
the  fact  helps  to  indicate  that  this  class  of  animals  has  its 
proper  affinities  with  the  ARTICULATA,  which  has  been 
denied  by  most  naturalists. 

The  form  is  curious.  Elevated  at  the  summit  of  a  long 
foot,  consisting  of  three  joints,  which  surmount  two  un- 
usually lengthened  and  slender  toes,  is  a  vase-shaped 
lorica,  which  is  three-sided.  Its  surface  is  covered  all 
over  with  minute  points,  very  closely  set,  so  that  it  re- 
sembles shagreen  ;  besides  which  it  forms  numerous  sharp 
ridges,  which  run  across  transversely.  The  two  sides  run 
off  into  thin  lateral  wings,  which  come  to  a  sharp  edge  ; 
the  back  angle  also  forms  a  ridge,  but  less  sharp  and  thin. 
In  front,  the  shell,  or  lorica,  is  as  it  were  cut  off  abruptly, 
like  the  rim  of  a  goblet,  but  out  of  this  rises  a  second 
column,  connected  with  the  rim  by  an  elastic  membrane, 
which  allows  some  freedom  of  motion.  This  column  is 
widely  divided  in  front  and  behind,  and  rises  to  a  point  on 
each  side.  When  the  rotatory  front  is  withdrawn,  these 
points  approach  and  meet,  closing  the  orifice  ;  but  when 
the  head  is  protruded  they  are  widely  separated. 

Internally,  we  see  the  usual  viscera  contained  in  so 
narrow  a  cavity  that  we  are  ready  to  suppose  the  walls  of 


WHEEL-BEARERS. 


243 


the  lorica  unusually  thick ;  this  is,  however,  an  optical 
illusion,  dependent  on  its  dilatation  into  those  angular 
wings  already  noticed.  The  cavity  penetrates  into  them  ; 
for  in  one  of  these  specimens  I  see  those  curious  twisted 
threads  that  are  believed  to  be  connected  with  respiration, 
within  the  lateral  wings.  The  stomachs  are  generally  full 
of  green  and  brown  food,  but  they  will  not  imbibe  car- 
mine. 


SKELETON  WHEBL-BKARER. 

Let  us  look,  however,  a  moment  longer  at  the  singular 
foot.     Between  the  first  and  second  joints  there  are  two 
projecting  spines  ;    these  differ  much  in  different  indivi- 
duals as  to  their  length,  slenderness,  and  direction  ;  some- 
B  2 


244  EVENINGS   AT    THE    MICROSCOPE. 

times  being  quite  short,  at  others  as  long  as  the  toes ; 
generally,  they  arch  downwards,  but  occasionally  they 
stand  out  straight,  or  even  curve  upwards.  In  some 
specimens  these  spines  appear  to  be  processes  of  the  first 
joint,  but  in  others  we  can  see  distinctly  that  they  belong 
to  a  little  intermediate  piece  between  the  first  and  second 
apparent  joints.  Between  the  two  toes,  on  the  hinder 
aspect,  projects  from  the  last  joint  a  small  spine,  which  is 
perhaps  the  rudiment  of  a  third  toe,  since  we  find  that 
number  in  some  genera  of  this  class.  The  whole  foot,  in- 
cluding the  toes,  is  rough  with  the  shagreen-like  points 
that  cover  the  lorica.  f 

You  have  already  noticed  the  rapidity  and  fitful  irre- 
gularity which  the  long  and  many-jointed  foot  confers 
upon  the  movements  of  this  curious  little  form.  From 
the  toe-tips,  as  a  point  of  adhesion,  it  throws  its  body  to 
and  fro,  or  from  side  to  side,  in  a  peculiar  manner.  The 
toes  are  sometimes  sprawled  out,  like  the  legs  of  an  ex- 
panded pair  of  compasses  ;  and  sometimes  the  joints  of  the 
foot  are  suddenly  bent  in  zig-zag  fashion,  and  then  as 
abruptly  straightened.  The  animal  swims  gracefully,  but 
only  with  moderate  swiftness,  the  rotatory  crown  of  cilia 
being  small,  though  forming  the  usual  vortices  when  the 
animal  is  moored :  while  thus  swimming,  the  toes  are 
gracefully  stretched  behind,  nearly  in  contact  with  each 
other.  It  is  lively  in  its  motions,  but  these  seem  per- 
formed without  any  ostensible  object ;  we  do  not  often  see 
it  attempt  to  eat,  or  nibble  at  any  substance. 

I  think  we  never  find  the  Skeleton  except  among  the 
sediment  at  the  bottom  of  the  water  in  which  it  is  kept ; 
among  which  also  we  frequently  see  the  remains  of  defunct 
specimens — the  skeleton  of  the  Skeleton ;  this  itself  makes 
a  pretty  object :  the  lorica,  with  its  point  and  ridges,  the 
thoracic  column,  the  foot  with  its  joints  and  spines,  and 
the  toes,  all  being  perfectly  preserved,  and  rendered  even 
more  clear  than  during  life,  because  of  the  removal  of  all 


WHEEL- BEARERS.  245 

the  soft  internal  parts  by  decay,  and  by  the  efforts  of 
those  little  scavengers,  the  smaller  species  of  infusorial 
animalcules.  These  quickly  find  their  way  into  the  interior 
of  any  dead  animal  with  a  shelly  case,  as  a  Wheel-bearer, 
a  Water-flea,  or  an  Insect,  and  soon  devour  every  particle 
of  soft  flesh,  cleaning  out  the  case  in  the  most  tidy 
'manner. 

Here  is  a  tiny  subject  which  will  test  your  powers  of 
observation,  and  possibly  your  patience,  in  satisfactorily 
denning  its  structure,  partly  on  account  of  its  swift  motion 
and  irregular  leaps,  and  partly  on  account  of  its  extreme 
transparency.  It  is  a  crystalline  cup,  somewhat  like  the 
body  of  a  wine-glass,  without  any  foot,  but  bearing  many 
flat  sword- shaped  processes,  which,  proceeding  from  the 
breast,  commonly  lie  flat  on  each  side,  down  the  body, 
the  points  projecting  below.  These  are  evidently  stiff  and 
highly  elastic,  and  their  use  is  manifest  to  any  one  who 
sees  the  creature  in  active  motion.  It  swims  with  a  rapid 
gliding  progress,  head  foremost,  but  at  almost  every  mo- 
ment it  makes  a  sudden  forcible  jerk  or" leap  backwards  or 
to  one  side,  and  that  so  quickly  that  the  eye  often  cannot 
follow  it  in  the  transition.  The  organs  by  which  these 
jumps  are  effected  are  the  long  breast- spines,  which  are 
suddenly  thrown  out  in  various  directions ;  and  they  may 
frequently  be  seen  extended  the  instant  after  a  leap.  When 
we  consider  that  the  creature  is  jerked  often  four  or  five 
times  its  own  length,  through  so  dense  a  fluid,  we  shall 
perceive  how  strong  the  muscular  action  must  be  which 
moves  the  lever-like  spines.  The  creature  is  thrown  irre- 
gularly, often  with  the  side  foremost,  or  the  back,  or  made 
to  perform  a  somersault  in  the  act.  It  is  probably  a  sensi- 
tiveness to  danger  or  annoyance  that  prompts  these  violent 
leaps ;  at  least,  it  frequently  performs  them,  after  a 
momentary  examination  of  any  floating  matter  with  which 
its  course  brings  it  into  contact. 

The  rotatory  organs,  the  source  of  the  common  gliding 


246  EVENINGS    AT    THE    MICROSCOPE. 

motion,  are  not  very  large  or  conspicuous;  the  cilia  appear 
to  be  set  all  along  the  brow.  The  eye  is  very  visible  : 
it  is  placed  near  the  front,  and  seems  to  be  of  a  deep 
bluish-black  hue. 

I  have  not,  however,  as  yet  introduced  the  nimble  little 
stranger  by  name.  We  may  call  it  familiarly  the  Sword- 
bearer,  but  Professor  Ehrenberg  has  named  it  Polyarthra 
platyptera. 

This  eminent  authority  on  all  that  concerns  these 
minute  forms  has  placed  the  species  among  those  which 
are  destitute  of  a  horny  lorica  or  shell.  But  he  is  cer- 
tainly in  error  here  ;  for,  as  you  may  see,  there  is  mani- 
festly a  stiff  lorica,  which  covers  the  back  and  sides,  but 
which  gapes  widely  in  the  middle  of  the  under  side, 
throughout  its  length.  From  the  lateral  points,  however, 
a  membrane  may  be  seen  for  a  short  distance,  which 
doubtless  protects  the  viscera  from  actual  exposure. 

The  sword-like  fins  appear  to  be  twelve  in  number,  ar- 
ranged in  groups,  or  bundles,  of  three  each ;  one  bundle 
being  set  on  each  side  of  the  dorsal,  and  one  on  each  side 
of  the  ventral  aspect,  at  about  one-fifth  of  the  entire 
length  from  the  frontal  points.  These  are  all  that  we  can 
ordinarily  count ;  but  I  have  seen  more ;  one  day,  while 
examining  a  specimen  that  presented  a  vertical  aspect  to 
me — end-on,  to  speak  familiarly — the  fins  being  all  ex- 
panded, I  saw  with  perfect  distinctness  a  seventh  pair, 
proceeding  from  the  middle  of  the  breast.  They  are  flat, 
thin,  narrow  blades,  of  exceeding  delicacy ;  all  distinctly 
serrated  on  both  edges,  the  teeth  pointing  from  the  base 
outward;  each  is  strengthened  by  a  central  rib.  They 
are  jointed  independently,  on  rounded  shelly  knobs,  and 
are  doubtless  moved  by  strong  muscles.  Under  pressure, 
the  knobs  and  the  fins  are  brought  out  with  beautiful  dis- 
tinctness. Here  again  we  have  true  jointed  limbs. 

On  the  front  you  may  discern  a  pair  of  tiny  antennae, 
each  bearing  a  pencil  of  very  fine  bristles.  And  just 


WHEEL-BEAREBS. 


247 


below  the  level  of  their  base,  in  the  centre  of  the  dorsal 
region,  you  see  the  large  eye,  of  a  deep  red  hue,  so  deep 
that  it  frequently  looks  as  if  it  were  actually  and  intensely 
black.  Just  below  the  eye,  apparently,  but  considerably 
more  towards  the  ventral  aspect,  there  is  a  huge  mastax, 
occupying  almost  half  the  length  of  the  whole  body.  The 
jaws  are  very  simple  in  their  construction,  and  therefore 
very  instructive,  for  they  contain  the  same  elements  as  in 
Brachionus;  but  from  their  excessive  tenuity,  and  for 
other  reasons  connected  with  the  form  of  the  animal,  they 
are  calculated  to  tax  to  the  utmost  your  perseverance  and 
skill  in  manipulation  to  resolve  them.  They  were  an 
enigma  to  me  for  years. 

The  great  mastax  is  pear-shaped,  pointing  obliquely 
towards  the  middle  of  the  belly.  This  form  is  owing  to 
the  great  length  of  foe  fulcrum,  and  the  wide  curvature  of 


SWORD-BEARER. 


the  mallei.  The  rami  are  very  broad,  somewhat  square 
at  their  base,  flat,  but  much  arched  longitudinally.  They 
open  and  shut  vigorously,  with  a  snapping  action,  but  are 


248  EVENINGS    AT    THE    MICROSCOPE. 

not  protruded  from  the  front ;  their  whole  interior  edges 
come  into  contact.  The  mallei  are  simple,  slender  bent 
rods,  apparently  without  distinct  articulation.  During  life 
they  are  thick  and  irregular  in  outline,  owing  to  their 
being  invested  with  dense  muscles ;  as  is  the  whole  upper 
portion  of  the  mastax.  These  muscles  conceal  or  disguise 
the  form  and  action  of  the  parts  during  life,  but  the  intro- 
duction of  a  drop  of  solution  of  potash  into  the  water  in- 
stantly dissolves  away  the  fleshy  parts,  leaving  the  solid 
organs,  or  those  composed  of  chitine,  beautifully  clear, 
and  fit  for  observation.  Without  this  aid  it  would  be  im- 
possible to  resolve  the  structure  of  these  minute  animals. 

The  little  Sword-bearer,  like  the  Brachionus,  carries  its 
eggs  attached  to  the  hinder  part  of  its  body,  for  some  time 
after  they  are  discharged ;  the  minute  green  oval  bodies 
that  you  see  sticking  to  the  side  of  this  specimen,  are  not, 
however,  eggs,  but  parasitic  animalcules  (Colacium  vesicu- 
losum),  which  very  frequently  infest  this  species,  adhering 
to  various  points  of  the  shell,  and  even  to  the  sword-fins. 

What  I  have  now  to  submit  for  your  examination  is  one 
of  the  rarest  species  of  the  class,  and  certainly  not  the 
least  singular  in  its  form.  It  is  the  tripod  Wheel-bearer 
(Actinurus  Neptunius).  When  fully  extended,  its  length 
exceeds  that  of  almost  every  other  species,  for  it  reaches 
about  one-twentieth  of  an  inch ;  but  its  extreme  thread-like 
slenderness  precludes  the  unassisted  eye  from  taking  cog- 
nizance of  it,  as  its  thickness,  even  when  greatest,  is  not 
more  than  one  six-hundredth  of  an  inch. 

From  this  excessive  length  and  tenuity,  the  appearance 
of  the  creature  is  very  remarkable.  It  may  be  likened  to 
a  cylindrical  tube,  out  of  which  protrude  a  great  number 
of  draw- tubes  from  both  extremities,  principally  the  pos- 
terior one.  Those  in  front  terminate  in  an  oval  proboscis, 
which  having  a  sort  of  finger  at  its  extremity,  and  two 
eyes,  with  an  antennal  tube  projecting  obliquely  back- 
wards, presents,  when  viewed  laterally,  a  strong  resem- 


WHEEL-BEARERS. 


249 


blanee  to  the  head  of  a  rabbit,  the  antenna  representing 
the  ears.  In  front,  and  just  below  this  head-like  proboscis, 
is  a  double  swelling,  containing  the  rotatory  organs,  which 
are  small  and  seldom  unfolded.  The  eyes  are  deep  black ; 
probably,  as  in  the  last  example,  a  red  of  great  intensity. 
When  the  head  is  withdrawn,  the 
integument  is  very  clearly  seen  to 
be  turned  inwards.  The  body  con- 
sists of  one  long  cylindrical  tube, 
which  receives  three  or  four  short 
joints  to  complete  the  abdomen ;  at 
the  dorsal  point  of  the  extremity  of 
the  last  of  these  is  the  cloaca ;  at 
this  part  the  diameter  is  already 
very  much  attenuated ;  but  there 
are  eight  or  nine  more  joints  which 
constitute  the  foot,  and  these  are  of 
extreme  slenderness.  Towards  the 
extremity,  two  processes  are  given 
off  behind,  each  consisting  of  a  club- 
shaped  piece,  with  a  slender  bristle 
at  the  tip.  The  foot  terminates  in  three  long,  slender, 
cylindrical,  divergent  toes,  which  are  flexible,  and  com- 
monly bent  outward ;  they  are  equal  in  thickness,  and 
truncate.  These  are  often  retracted  in  various  degrees, 
even  when  the  foot  is  otherwise  extended. 

Owing  to  the  slenderness  of  the  body,  the  viscera  are 
greatly  elongated.  The  mastax,  as  usual  in  this  family, 
consists  of  two  hemispheres  (each  bearing  two  teeth,  set 
transversely,  but  converging  to  the  centre) ;  it  is  situated 
at  a  considerable  distance  from  the  wheels,  and  is  reached 
by  a  long  buccal  funnel.  The  digestive  canal  is  a  long 
sac,  apparently  undivided  ;  it  originates  directly  from  the 
mastax,  with,  I  think,  two  small  basal  glands;  its  pos- 
terior extremity  becomes  gradually  tapered  to  the  cloaca. 
In  the  specimen  we  are  examining,  a  small  quantity  of 


TRIPOD   WHEEL-BEARER. 


250  EVENINGS    AT    THE    MICBOSCOPE. 

faecal  matter  of  a  yellowish-brown  colour  is  collected  in  two 
small  masses,  near  the  extremity.  Along  the  under  side 
runs  the  ovary,  which  in  this  specimen  contains  two  long 
oval  eggs  in  advanced  development ;  from  their  transpa- 
rent brightness,  I  suspect  the  young  are  produced  before 
birth.  I  think  I  can  detect  a  contractile  bladder,  but  am 
not  certain. 

The  dorsal  region  of  the  trunk  is  marked  with  strong 
rugged  lines  running  longitudinally  ;  these  look  like  corru- 
gations of  the  integument,  but  I  incline  to  think  them  the 
strongly  developed  muscles  for  the  retractation  of  the  foot. 
Muscles  are  seen  running  through  the  joints  of  the  foot, 
until  they  can  no  longer  be  traced,  from  their  tenuity, 
The  viscera  can  be  detected  with  difficulty,  partly  owing 
to  the  longitudinal  muscles,  which  are  so  strong  and  close, 
and  partly  from  the  incessant  contraction  and  elongation 
of  the  parts,  which  drive  the  internal  organs  hither  and 
thither.  It  refuses,  you  see,  to  swallow  carmine,  which 
might  have  assisted  us. 

This  singular  animal  is  lively  in  its  motions,  especially 
in  the  protrusion  and  retractation  of  the  extremities.  These 
are  constantly  alternating,  and  a  very  curious  sight  it  is  to 
see  the  immense  length  of  foot  suddenly  thrust  forth  from 
the  body,  in  which  it  had  been  completely  hidden,  the 
starting  out  of  the  horizontal  processes,  and  the  diverging 
of  the  long  toes,  as  these  are  successively  uncovered.  The 
latter  do  not  seem  to  be  often  used  as  instruments  of  pre- 
hension or  adhesion.  Indeed,  the  animal  does  not  appear 
very  much  given  to  change  of  place,  but  lies  in  the  water, 
alternately  contracting  and  elongating.  Frequently,  as  the 
foot  is  thrust  out,  the  body  is  made  to  bend  forward  so  as 
to  form  a  right  angle  (see  the  engraving,  in  which  the 
animal  is  thus  represented  at  a ;  b  represents  it  when  the 
head  is  rotating,  but  the  foot  is  almost  wholly  withdrawn 
within  the  body;  in  which  state  the  resemblance  to  a 
telescope,  or  to  a  nest  of  glass  tubes,  is  striking). 


WHEEL-BEABEBS.  251 

The  last  specimen  of  this  class  of  tiny  favourites  that  I 
shall  show  you  is  one  of  more  than  ordinary  beauty.  It 
is  the  Two-lipped  Tube-wheel  of  the  Hornwort  (Limnias 
ceratophylli).  Hitherto  we  have  seen  such  examples  as 
have  the  power  of  freely  swimming  from  place  to  place  at 
pleasure ;  but  there  is  a  considerable  group,  of  which  this 
is  a  member,  which  are  permanently  stationary,  being 
fixed  for  life  to  the  leaves  or  stems  of  the  vegetation  that 
grows  under  water.  The  stiff  and  spinous  whorls  of  the 
Hornwort  (Ceratophyllum  demersum),  that  grows  commonly 
in  sluggish  streams  and  pasture-pools,  is  a  favourite  resort 
of  the  species,  but  it  is  not  confined  to  any  one  plant. 
Here,  for  instance,  it  has  chosen  as  the  site  of  its  resi- 
dence the  much -cleft  leaves  of  the  Water  Crowfoot  (Ra- 
muiculus  aquatilis) ;  those  leaves,  I  mean,  which,  growing 
wholly  under  the  water,  are  divided  into  a  multitude  of 
slender  finger-like  filaments,  so  different  from  those  which 
float  on  the  surface,  and  which  are  merely  notched. 

You  can  readily  find  the  Tube-wheels  by  the  aid  of  a 
pocket  lens,  and  even  with  the  naked  eye  when  you  have 
seen  one  or  two.  By  holding  up  this  phial,  in  which  a 
little  plant  of  the  Crowfoot  is  growing,  and  searching,  with 
the  lens,  the  window  being  in  front  of  you,  the  filaments 
one  by  one,  you  will  readily  perceive,  here  and  there, 
little  shining  objects  standing  up,  or  projecting  in  various 
directions  from  the  surface  of  the  leaves.  The  colony  is 
rather  numerous  in  this  case,  and  we  shall  have  no  diffi- 
culty in  selecting  our  specimens. 

On  this  filament,  which  I  have  seized  with  the  tips  of  a 
pair  of  pliers,  I  can  see  at  least  half-a-dozen  of  the  little 
parasites.  This,  then,  I  will  nip  off  from  the  plant,  and 
put  it  with  its  tiny  population  into  the  live-box.  Here  it 
is  ready  for  examination. 

Several  of  the  animals  are  in  the  field  of  view ;  but  we 
will  look  at  one  at  a  time.  A  long  narrow  tube,  slightly 
widening  at  the  mouth,  is  affixed  by  the  lower  extremity 


252 


EVENINGS    AT    THE    MICROSCOPE. 


to  the  slender  filaments  of  water-grass,  crowfoot,  &c.  It 
is  about  one  fifty-fifth  of  an  inch  in  length,  pellucid,  but 
tinged  with  brownish  yellow.  It  appears  to  be  of  a  gela- 
tinous texture,  and  is  covered  with  foreign  substances, 
such  as  decaying  animal  or  vegetable  mat- 
ters, which  adhere  to  its  surface.  From 
the  mouth  of  the  tube  protrudes  a  trans- 
parent colourless  animal,  the  head  of  which 
is  rounded,  with  the  extremity  pursed  up. 
Suddenly  it  unfolds  its  flower-like  wheel, 
which  consists  of  two  broad  nearly  circular 
lobes  united,  the  margin  of  which  is  set 
with  strong  cilia,  much  resembling  those  of 
the  last  species. 

Each  cilium  appears  to  be  curved,  and 
to  be  thickened  at  the  middle — the  optical 
expression  of  the  ciliary  wave ;  and  the 
effect  of  the  rotation,  as  each  seems  to 
pursue  its  fellows  around  the  circular 
course  down  the  dividing  sinuosity,  up  the 
opposite  sides,  and  round  the  margin  again, 
is  very  striking.  The  cilia  at  the  front 
are  interrupted  between  the  lobes.  In 
the  centre  of  each  lobe  is  a  broad  plate, 
surrounded  by  a  bright  ring,  and  crossed 
by  radiating  lines,  which  also  extend  to- 
wards the  ciliated  margin ;  probably  these  are  muscular 
filaments.  The  funnel  is  between  the  lobes,  and  leads  by 
a  short  oesophagus,  or  gullet,  to  a  bulbous  transparent 
mastax,  in  which  are  seen  jaws  that  work  on  each  other. 
Below  this  is  a  long  capacious  sac,  without  convolutions 
or  constrictions,  but  apparently  granular  in  its  texture. 
The  alimentary  canal  is  bent  upwards  through  the  whole 
length,  terminating  in  an  orifice  behind  the  rotatory  organ  ; 
for  though  I  have  not  traced  it  when  empty,  I  have  seen 
the  fa3cal  matter  driven  rapidly  upward  as  through  a  canal, 


TWO-LIl'PED 
TUBE-WHEEL. 


WHEEL-BE  AREBS.  258 

until  the  mass  was  discharged  just  behind  the  sinuous 
cleft.  On  our  mixing  carmine  with  the  water,  the  effect  is 
very  striking ;  the  particles,  whirled  round  in  two  circular 
vortices,  are  poured  in  an  accumulated  torrent  through  the 
sinuosity,  and  over  the  elevation  at  the  front  of  the  head. 
We  presently  perceive  a  slender  line  of  crimson  passing 
down  below  the  mastax,  which  indicates  a  slender  stomach- 
tube  there ;  and,  after  a  while,  a  little  bah1  of  the  same 
pigment  accumulates,  and  is  seen  resting  a  little  lower 
down.  This,  then,  indicates  the  form  and  position  of  the 
stomach ;  it  must  be  a  very  slender  canal,  terminating  in 
a  small  rounded  bag,  at  about  one-third  of  the  distance 
from  the  mastax  to  the  base  of  the  tube.  The  lengthened 
sac  which  you  see  is  the  ovary,  from  which  the  eggs  are 
discharged  into  the  lower  part  of  the  case. 


WHEELS   OF   TVER-WHEEL. 


The  mouth  needs  a  little  explanation  in  detail.  As  you 
see  it,  you  probably  discern  little  resemblance  in  its  parts 
to  the  same  organ  in  Brachionus,  and  yet  essentially  it  is 
formed  of  the  very  same  parts  ;  and  as  it  is  very  instruc- 
tive to  observe  the  modifications,  in  different  animals,  of  a 
common  model  of  any  particular  organ,  it  will  be  worth 
while  to  devote  a  few  minutes'  careful  observation  to  this 
structure  before  us,  especially  as  it  is  here  seen  with  more 
than  usual  brilliancy  and  clearness. 

The  mastax,  then,  which  you  see  in  the  centre  of  the 


254  EVENINGS    AT    THE    MICROSCOPE. 

animal,  just  below  the  level  of  the  beautiful  flower-like 
wheels,  consists  as  usual  of  three  sub -globose  lobes  ;  one 
on  each  side  appropriated  to  each  malleus,  and  the  third 
descending  towards  the  ventral  aspect,  which  envelops 
the  incus.  The  mallei  are  more  intimately  united  to  the 
rami  of  the  incus  than  in  the  former  type,  each  uncus 
forming,  with  its  ramus,  a  well-defined  mass  of  muscle, 
inclosing  the  solid  parts,  and  in  form  approaching  that  of 
a  quadrant,  or  fourth  part  of  a  circle  ;  two  flat  faces 
opposing  and  working  on  each  other.  Across  the  upper 
surface  of  the  mass  the  uncus  is  stretched,  as  three  long 
parallel  fingers  arched  in  their  common  direction,  and  im- 
bedded in  the  muscular  substance  ;  their  points  just  reach- 
ing the  opposite  face  of  the  ramus,  and  meeting  the  points 
of  the  opposite  uncus,  when  closed.  The  manubrium  is 
much  disguised,  by  being  greatly  dilated  transversely, 
forming  three  bow-like  loops  of  little  solidity,  to  the  chord 
of  which  the  fingers  are  soldered,  not  articulated.  The 
surface  of  the  dense  muscular  mass  displays  striae,  or 
streaks,  parallel  to  the  fingers,  and,  as  it  were,  continuing 
their  number  towards  their  dorsal  extremity,  becoming 
fainter  till  they,  are  imperceptible.  These  striae  do  not 
disappear  when  the  muscular  parts  are  dissolved  by  potash  ; 
and  hence  I  infer  the  existence  of  a  delicate  investiture  of 
solid  substance  similar  to  that  of  the  teeth,  &c.,  inclosing 
the  muscular  mass. 

The  incus,  which  cannot  be  separated  from  the  mallei, 
thus  consists  of  two  portions,  corresponding  to  the  rami  in 
Brachionus,  &c.,  each  of  which  forms  the  lower  part  of  the 
mass  just  described.  At  the  ventral  extremity  they  are 
articulated  to  a  slender  fulcrum,  which  is  a  little  bent 
downward.  The  solid  framework  of  each  ramus  sends  off 
from  its  inferior  surface  a  slender  curved  process,  which  is 
connected  with  the  extremity  of  the  fulcrum. 

The  action  of  this  apparatus  is  as  follows  : — The  ciliary 
vortices  produced  by  the  waves  of  the  coronal  disk,  pass 


WHEEL-BEAREBS.  255 

together  through  the  upper  sinus,  and  are  hurled  in  one 
stream  along  the  centre  of  the  face,  nearly  to  the  project- 
ing chin.  Here  is  placed  the  orifice  of  the  buccal  funnel, 
a  perpendicularly  descending  tube  of  considerable  width, 
slightly  funnel-shaped  at  the  top,  the  interior  surface  of 
which  is  strongly  ciliated.  It  descends  straight  upon  the 
mastax,  over  the  part  where  the  unci  unite.  But  just 
above  this  point  there  are  two  valves  projecting  from  the 
walls  of  the  tube,  also  well  ciliated.  These  can  be  brought 
into  contact,  or  separated  in  various  degrees,  at  will ;  and, 
being  very  sensitive,  they  regulate  the  force  of  the  inflow- 
ing current,  and  doubtless  exclude  hurtful  or  useless  sub- 
stances. The  current  now  flows  along  the  two  rami  of  the 
incus,  as  I  have  already  described ;  and,  passing  between 
their  separated  points,  descends  into  the  oesophagus,  a 
slender  duct  opening  beneath  them,  and  leading  to  the 
digesting  stomach. 

As  this  current  passes,  the  manducatory  apparatus  acts 
upon  the  particles  of  food  which  it  brings  in  its  course. 
The  quadrant- shaped  masses  approach  each  other  and 
recede,  with  a  rapid  rolling  movement,  in  the  direction  of 
the  curvature  of  the  mallei ;  while,  at  the  same  time,  the 
rami  of  the  incus  open  and  close  their  points,  rise  and 
sink,  and  occasionally  perform  a  kind  of  shovelling  action. 
The  points  of  the  fingers  of  the  unci,  meeting  each  other, 
doubtless  pierce  and  tear  the  Infusoria  swallowed,  and  the 
striated  faces  bruise,  squeeze,  and  grind  them  down. 

When  the  muscular  investment  is  dissolved  away  by 
potash,  the  essential  identity  of  the  whole  structure  with 
that  of  the  type  already  described  becomes  abundantly 
evident.  Even  the  mallei,  which  in  some  aspects  present 
difficulty,  when  viewed  vertically,  are  but  little  changed  ; 
the  fingers  are  parallel  instead  of  divergent,  and  the  handle- 
like  character  of  the  manubrium  is  lost ;  but  three  areas, 
inclosed  by  loops  or  carinae  of  solid  substance,  reveal  their 
true  nature. 


256  EVENINGS    AT    THE    MICROSCOPE. 

We  will  now  see  if  we  can  separate  the  animal  from  its 
tube,  so  as  to  examine  its  lower  parts.  By  a  gentle  pres- 
sure upon  the  bottom  of  the  tube  with  the  edge  of  a  pen- 
knife, which  I  bring  to  bear  upon  it  by  the  aid  of  this 
simple  microscope,  the  creature  is  induced  to  wriggle  out 
of  his  case.  Beplacing  now  the  cover  of  the  live-box, 
and  placing  it  again  on  the  stage  of  the  compound  micro- 
scope, we  see  that  the  lower  part  of  the  body  forms  a  foot 
analogous  to  that  of  a  Brachiomis,  covered  with  ring-like 
wrinkles,  and  separated  from  the  body  by  an  abrupt  con- 
striction and  diminution  of  the  diameter.  At  the  very  ex- 
tremity there  is  a  sort  of  sucking-disk,  by  which  we  may 
presume  the  hold  of  the  animal  upon  the  plant  is  main- 
tained. No  organic  connection  subsists  between  the  foot 
and  the  tube  ;  for  the  latter  is  not  an  essential  part  of  the 
animal,  though  absurdly  called  a  lorica  by  Ehrenberg,  but 
only  an  accumulation  of  mucus  successively  exuded  from 
the  body,  and  thrown  off  in  the  form  which  it  possesses  by 
the  contractions  and  other  movements  of  the  body. 

But  see !  the  poor  naked  creature  is  writhing  in  con- 
tortions, which  become  more  and  more  convulsive  and 
spasmodic  :  and  now  it  evinces  great  rigidity  in  these,  till 
the  body  has  become  almost  shapeless,  portions  of  the 
surface  being  here  and  there  violently  forced  out  into  pro- 
jections, and  the  foot  strongly  curled  up.  The  only  signs 
of  life  that  now  remain  are  the  occasional  fitful  workings 
of  the  jaws.  Are  we  then  to  suppose  that  the  shelter  of 
the  gelatinous  case  is  needful  to  its  continued  existence  ?  or 
did  I  inflict  a  mortal  injury  upon  it  when  I  laid  the  edge  of 
my  penknife  upon  its  lower  part  to  drive  it  forth  ?  Most 
probably  the  latter  is  the  true  solution. 

Out  of  the  colony  that  remains,  we  will  now  select 
another  specimen,  with  ripening  eggs,  in  order  to  watch 
the  development  of  the  young.  Here  is  one  with  three 
eggs  lying  obliquely  in  the  tube,  one  of  which  is  already 
showing  the  impatient  movements  of  the  embryo  within. 


WHEEL-BEARERS.  257 

Ha !  now  the  egg-shell  has  burst,  and  the  little  creature 
escapes  from  its  prison,  and  quickly  makes  its  way  to  the 
mouth  of  the  parent-tube.  Now  it  is  free,  and  swims 
away  rapidly,  in  a  giddy,  headlong  manner.  It  is  quite 
unlike  its  mother ;  for  its  form  is  trumpet-shaped,  re- 
sembling that  of  a  Stentor  with  a  wreath  of  cilia  around 
the  head,  interrupted  at  two  opposite  points:  the  central 
portion  of  the  head  rises  into  a  low  cone.  There  is  as  yet 
no  trace  of  the  beautiful  double-petalled  flower. 

It  has  been  whirling  giddily  about  the  live-box  for  about 
a  quarter  of  an  hour,  but  now  it  begins  to  manifest  tokens 
of  weariness  ;  or  rather  the  time  is  approaching  for  it  to 
select  a  place  of  permanent  sedentary  abode.  Its  motion 
is  sensibly  retarded ;  it  now  and  then  adheres  to  the  glass 
momentarily,  by  its  foot,  and  moves  forward  by  successive 
jerks,  not  proceeding  more  than  its  own  length  at  a  time, 
and  this  apparently  with  effort.  The  periods  of  its  re- 
maining stationary  become  longer,  so  that  you  may  sup- 
pose it  finally  settled  twice  or  thrice,  before  its  wanderings 
are  quite  over,  some  shock  or  alarm  sending  it  off  to  a 
little  distance  again. 

At  length  it  wanders  no  more ;  its  foot  holds  fast  to  the 
glass,  and  its  movements  are  confined  to  whirlings  round 
and  round  on  this  as  a  pivot,  and  to  sudden  contractions 
of  length.  Presently  we  see  a  very  delicate  film  surround- 
ing the  point  of  attachment ; — the  first  rudiment  of  the 
tube,  a  ring  of  mucus  thrown  off  from  the  skin,  and 
pressed  down  to  the  foot  by  the  contractions  of  the  body. 
Meanwhile,  the  ciliary  crown  is  dividing  itself  into  two, 
and  now  we  see  already  the  essential  form  and  appearance 
of  the  mature  animal,  every  moment  developing  its  per- 
fection. 


258  EVENINGS   AT    THE    MICBOSCOPE. 


CHAPTER  XV. 

WORMS. 

AN  examination  of  the  diverse  modes  in  which  locomotion 
is  performed  among  animals,  and  the  various  organs  and 
modifications  of  organs  that  subserve  this  important  pur- 
pose, would  form  no  uninteresting  chapter  in  natural 
history.  You  have  two  feet,  your  dog  has  four;  in  the 
bird,  two  of  these  are  converted  into  wings,  with  which  it 
rises  into  the  air ;  in  the  fish  all  of  them  are  become  fins, 
with  which  it  strikes  the  water.  But  it  is  in  the  inverte- 
brate classes  that  we  discover  the  strongest  variations. 
The  Poulpe  "  flops  "  awkwardly  but  vigorously  along,  by 
the  alternate  contractions  and  expansions  of  the  web  that 
unites  its  arm ;  the  Snail  glides  evenly  over  the  herbage 
by  means  of  its  muscular  disk ;  the  Scallop  leaps  about  by 
puffs  of  water  driven  from  its  appressed  lips  ;  the  Lobster 
shoots  several  yards  in  a  second  by  the  blow  of  its  tail 
upon  the  water ;  the  Gossamer  Spider  floats  among  the 
clouds  upon  a  balloon  that  it  has  spun  from  its  own  body ; 
the  Centipede  winds  slowly  along  upon  a  "  hundred"  pairs 
of  feet ;  the  Beetle  darts  like  an  arrow  upon  three ;  and 
the  Butterfly  sails  on  the  atmosphere  with  those  painted 
fans  which  are  properly  "  aerial  gills."  How  elegantly 
does  the  Planaria  swim  by  the  undulation  of  its  thin 
body,  and  the  Medusa  by  the  pumping  forth  of  the  water 
held  within  its  umbrella !  How  wondrously  does  the 
Echinus  glide  along  the  side  of  the  tank  on  its  hundreds 
of  sucking- disks !  How  beautiful,  and  at  the  same  time 
how  effective,  are  the  ciliary  wheels  of  the  Brachionus ! 


WOBMS.  259 

I  am  now  going  to  show  you  some  other  examples  of 
travelling  machinery  in  an  humble  and  despised,  but  far 
from  uninteresting,  class  of  animals, — the  Worms.  Here 
is  an  Earth-worm  upon  the  garden-border.  With  what 
rapidity  it  winds  along,  and  now  it  pokes  its  sharp 
nose  into  the  ground,  and  now  it  has  disappeared !  If 
your  eye  could  follow  it,  you  would  see  that  it  makes  its 
way  through  the  compact  earth  not  less  easily  nor  less 
rapidly  than  it  wound  along  the  surface.  If  you  take  it 
into  your  hand,  you  perceive  no  feet,  wings,  fins,  or  limbs 
of  any  kind ;  only  this  long  cylinder  of  soft  flesh,  divided 
into  numerous  successive  rings,  and  tapering  to  each  ex- 
tremity. The  very  snout  which  you  saw  enter  so  easily 
into  the  substance  of  the  soil,  is  no  hard  bony  point,  but 
formed  of  the  same  soft  yielding  flesh  as  the  other  parts. 
And  yet  with  no  other  implement  does  the  lithe  worm 
penetrate  whithersoever  it  will  through  the  ground.  How 
does  it  effect  this  ? 

The  fineness  of  the  point  to  which  the  muzzle  can  be 
drawn  is  the  first  essential.  This  can  be  so  attenuated 
that  the  grains  of  adherent  soil  can  readily  be  separated 
by  it,  when  its  action  becomes  that  of  the  wedge.  The 
body  being  drawn  into  the  crevice  thus  made,  the  particles 
are  separated  still  farther.  Now  another  provision  comes 
in ;  the  whole  surface  of  the  skin  secretes  and  throws  off  a 
quantity  of  tenacious  mucus  or  slime,  as  you  will  imme- 
diately perceive  if  you  handle  the  Worm  ;  this  has  the 
double  effect  of  causing  the  pressed  particles  of  soil  to  ad- 
here together,  and  then  to  form  a  cylindrical  wall,  of  which 
they  are  the  bricks,  and  the  slime  the  mortar ;  and  also  of 
greasing,  as  it  were,  the  whole  interior  of  the  burrow  or 
passage  thus  made,  so  that  the  Worm  can  travel  to  and 
fro  in  it  without  impediment ;  while  the  fact  that  the 
slime  is  continually  poured  forth  afresh  prevents  the  least 
atom  of  earth  from  adhering  to  its  body.  This  you  have 
doubtless  observed,  or  may  observe  in  a  moment,  if  you 
s2 


260  EVENINGS   AT    THE    MICKOSCOPE. 

will  take  the  trouble  to  thrust  a  spade  into  the  ground,  and 
give  it  two  or  three  shakes.  You  will  presently  see  on  all 
sides  the  alarmed  Earth-worms  coming  swiftly  to  the 
surface,  and  will  notice  how  perfectly  sleek  and  clean 
they  are. 

But  these  contrivances  are  only  accessories  :  we  have 
not  yet  discovered  the  secret  of  the  easy  movement.  The 
mere  elongation  of  the  snout  is  no  explanation  of  the  dis- 
appearance of  the  Worm  in  the  burrow  ;  for  you  will 
naturally  and  reasonably  say  that  this  elongation  cannot 
extend  beyond  a  certain  limit ;  and  what  then  ?  No  fur- 
ther progress  can  be  made  unless  the  hinder  parts  of  the 
body  are,  by  contraction,  drawn  up  towards  the  elongated 
front ; — but  what  holds  the  front  in  place  meanwhile  ?  Why, 
when  the  muscles  contract,  does  not  the  taper,  wedge- 
like  muzzle  slip  back  and  lose  the  ground  it  had  gained  ? 

This  we  will  now  look  at.  I  take  up  this  Worm,  and 
put  it  into  a  narrow  glass  cell,  where  we  may  watch  its 
movements.  It  presently  begins  to  elongate  and  contract 
its  body  vigorously,  apparently  alarmed  at  its  unwonted 
position ;  and  the  mucus  is  thrown  off  in  copious  abund- 
ance. We  apply  a  low  microscopic  power  to  it,  and  catch 
glimpses,  now  and  again,  as  it  writhes  about,  of  a  number 
of  tiny  points  protruded  and  retracted  with  great  regularity 
through  the  skin.  Its  mobility  precludes  our  discerning 
much  more  than  that  these  points  are  very  numerous,  that 
they  are  arranged  in  four  longitudinal  lines,  running  along 
the  ventral  side  of  the  animal, — two  lines  on  each  side, — 
and  that  in  each  line  there  is  a  point  protruded  from  each 
of  the  many  rings  of  which  the  Worm's  body  is  made  up. 

In  order  to  see  a  little  more  of  these  organs  we  must 
sacrifice  a  Worm  ;  having  killed  it,  and  divided  the  body 
in  the  middle,  I  cut  off,  with  sharp  scissors,  a  small  trans- 
verse portion,  say  two  or  three  rings,  and  press  the 
fragment  between  plates  of  glass.  Now,  with  a  higher 
magnifying  power,  we  discern  in  the  midst  of  the  trans- 


WOBMS.  261 

lucent  flesh  the  points  in  question.  They  are  not,  how- 
ever, single ;  but  each  protrusile  organ  consists  of  a  pair 
of  transparent,  brittle,  glassy  rods,  shaped  like  an  italic  /, 
of  which  the  recurved  points  are  directed  backwards  when 
thrust  out  from  the  skin. 

The  mode  in  which  these  assist  the  progression  of  the 
Worm  is  well  described  by  Professor  Bymer  Jones. 
"  The  attenuated  rings  in  the  neighbourhood  of  the  mouth 
are  first  insinuated  between  the  particles  of  the  earth, 
which,  from  their  conical  shape,  they  penetrate  like  a 
sharp  wedge ;  in  this  position  they  are  firmly  retained  by 
the  numerous  recurved  spines  appended  to  the  different 
segments ;  the  hinder  parts  of  the  body  are  then  drawn 
forward  by  a  longitudinal  contraction  of  the  whole  animal 
— a  movement  which  not  only  prepares  the  creature  for 
advancing  further  into  the  soil,  but,  by  swelling  out  the 
anterior  segments,  forcibly  dilates  the  passage  into  which 
the  head  had  been  already  thrust;  the  spines  upon  the 
hinder  rings  then  take  a  firm  hold  upon  the  sides  of  the 
hole  thus  formed ;  and,  preventing  any  retrograde  move- 
ment, the  head  is  again  forced  through  the  yielding 
mould ;  so  that,  by  a  repetition  of  the  process,  the  animal 
is  able  to  advance  with  the  greatest  apparent  ease  through 
substances  which  it  would  at  first  seem  utterly  impossible 
for  so  helpless  a  being  to  penetrate."  * 

Implements  analogous  to  these  are  found  in  most  of  the 
animals  of  the  class  Annelida,^  to  which  the  Earth-worm 
belongs.  But  in  this  creature  you  see  them  in  their  sim- 
plest form  :  it  is  to  the  aquatic  Worms  that  you  must  look 
if  you  wish  to  see  the  amazing  diversity,  complexity,  and 
delicacy  of  these  organs.  In  these  there  are  one  or  two 
pairs  of  "feet"  on  each  ring,  consisting  of  wart-like  pro- 
minences, which  are  perforate  and  protrusile,  and  through 

*  «  Gen.  Outline,"  202. 

f  From  the  Latin  annellus,  a  little  ring.  A  large  class  of  animals 
known  under  the  common  name  of  Worms, 


262  EVENINGS   AT    THE    MICBOSCOPE. 

the  middle  of  which  work  a  number  of  bristles  (seta), 
arranged  in  a  radiating  pencil,  something  like  the  hairs  of 
a  paint-brush.  In  this  transparent  and  colourless  little 
Nais  from  fresh  water,  you  may  see  their  form  and  arrange- 
ment ;  in  complexity  they  present  an  advance  upon  the 
Earth-worm,  for  here  there  are  some  seven  or  eight  bristles 

in  each  pencil,  which  radiate 
in  the  same  plane,  and  are 
graduated  in  length  ;  they  are 
very  slender,  bent  at  the  tip, 
and  as  transparent  as  if  drawn 
out  of  spun  glass.  It  is  inter- 
esting to  observe  with  what 
lightning-like  rapidity  they  are 
FOOT  OP  NAIS  thrust  out  and  withdrawn  in 

constant    succession,    as    the 
body  is  ever  lengthening  and  shortening. 

Let  us  exchange  this  little  fresh-water  Worm  for  a 
marine  one.  Here  is  a  Polynde,  a  curious  genus,  very 
common  under  stones  at  low  water  on  our  rocky  shores. 
It  is  remarkable  on  several  accounts.  All  down  the  back 
we  discover  a  set  of  oval  or  kidney-shaped  plates,  which 
are  called  the  back-shields  (dorsal  elytra) ;  these  are  flat. 
and  are  planted  upon  the  back  by  little  foot-stalks,  set  on 
near  the  margin  of  the  under  surface :  they  are  arranged 
in  two  rows,  overlapping  each  other  at  the  edge.  These 
kidney-shaped  shields,  which  can  be  detached  with  slight 
violence,  are  studded  over  with  little  transparent  oval 
bodies,  set  on  short  foot-stalks  which  are  perhaps  delicate 
organs  of  touch.  The  intermediate  antennae,  the  tentacles, 
and  the  cirri,  or  filaments  of  the  feet,  are  similarly  fringed 
with  these  little  appendages,  which  resemble  the  glands  of 
certain  plants,  and  have  a  most  singular  appearance.  If 
we  remove  the  shields,  we  discover,  on  each  side  of  the 
body,  a  row  of  wartlike  feet,  from  each  of  which  project 
two  bundles  of  spines  of  exquisite  structure.  The  bundles, 


WORMS.  263 

expanding  on  all  sides,  resemble  so  many  sheaves  of 
wheat ;  or  you  may  more  appropriately  fancy  you  behold 
the  armoury  of  some  belligerent  sea-fairy,  with  stacks  of 
arms  enough  to  accoutre  a  numerous  host.  But  if  you 
look  closely  at  the  weapons  themselves,  they  rather  re- 
semble those  which  we  are  accustomed  to  wonder  at  in 
missionary  museums, — the  arms  of  some  ingenious  but 
barbarous  people  from  the  South  Sea  Islands, — than  such 
as  are  used  in  civilised  warfare.  Here  are  long  lances, 
made  like  scythe-blades,  set  on  a  staff,  with  a  hook  at  the 
tip,  as  if  to  capture  the  fleeing  foe  and  bring  him  within 
reach  of  the,  blade.  Among  them  are  others  of  similar 
shape,  but  with  the  edge  cut  into  delicate  slanting  notches, 
which  run  along  the  sides  of  the  blade  like  those  on  the 
edge  of  our  reaping-hooks.  These  are  chiefly  the  weapons 
of  the  lower  bundle  ;  those  of  the  upper  are  still  more  im- 
posing. The  outmost  are  short  curved  clubs,  armed  with 
a  row  of  shark's  teeth  to  make  them  more  fatal;  these 
surround  a  cluster  of  spears,  the  long  heads  of  which  are 
furnished  with  a  double  row  of  the  same  appendages,  and 
lengthened  scymitars,  the  curved  edges  of  which  are  cut 
into  teeth  like  a  saw.  Though  a  stranger  might  think  I 
had  drawn  copiously  on  my  fancy  for  this  description,  I 
am  sure,  with  your  eye  upon  what  is  on  the  stage  of  the 
microscope  at  this  moment,  you  will  acknowledge  that  the 
resemblances  are  not  at  all  forced  or  unnatural.  To  add 
to  the  effect,  imagine  that  all  these  weapons  are  forged  out 
of  the  clearest  glass  instead  of  steel ;  that  the  larger  bun- 
dles may  contain  about  fifty,  and  the  smaller  half  as  many, 
each  ;  that  there  are  four  bundles  on  every  segment,  and 
that  the  body  is  composed  of  twenty-five  such  segments  ; 
and  you  will  have  a  tolerable  idea  of  the  garniture  and 
armature  of  this  little  Worm,  that  grubs  about  in  the  mud 
at  low-water  mark. 

Should  it  ever  be  your  fortune  to  fall  in  with  a  species 
of   Sea-mouse    (Aphrodite    hystrix),    which   inhabits   our 


264  EVENINGS   AT    THE    MICROSCOPE. 

southern  coast  a  little  way  from  the  shore,  you  may  be 
delighted  and  surprised  with  a  modification  of  these 
organs,  which  exhibits  a  more  than  ordinarily  obvious 
amount  of  creative  forethought  and  skill.  I  will  describe 
them  in  the  words  of  the  learned  historians  of  these 
animals,  MM.  Audouin  and  Milne-Edwards  : — 

"  The  feet  are  divided  into  two  very  distinct  branches, 
the  lower  of  which  is  large,  conical,  of  a  yellowish-brown 
hue,  and  much  shagreened  on  the  surface.  The  upper 
branch  is  much  less  salient  than  the  lower.  We  observe 
at  the  foot  of  the  dorsal  shields  two  bundles  of  rigid  bris- 
tles :  the  one,  expanded  like  a  fan  and  applied  upon  the 
shields,  is  fixed  immediately  outside  the  insertion  of  those 
organs ;  the  bristles  which  compose  it  are  awl-shaped, 
without  teeth,  slightly  curved,  and  directed  inwards  and 
backwards;  their  colour  is  a  clear  brown,  with  golden 
reflections.  The  second  bundle  is  inserted  more  exter- 
nally, on  a  tuberculous  footstalk,  and  points  horizontally 
backwards  and  outwards.  The  bristles  which  enter  into 
its  composition  are  very  long,  very  strong,  and  terminated 
by  a  lance-shaped  point,  of  which  the  edges  are  garnished 
with  teeth  curved  backwards  towards  the  base.  These  are 
veritable  barbed  arrows,  having  the  extremities  sometimes 
exposed,  but  often  concealed  in  a  sheath  which  is  formed 
of  two  horny  pieces,  capable  of  opening  and  of  closing 
again  upon  them. 

"  The  use  of  these  two  valves  it  is  not  difficult  to  detect. 
They  protect  the  points  of  the  arrow,  and  permit  the 
Aphrodite  to  receive  them  again  into  its  body  unharmed  ; 
whereas,  without  this  precaution,  the  tissues  which  they 
traverse  would  be  cut  and  mangled.  But  when  these 
weapons  are  deeply  plunged  into  a  foreign  body,  as  into 
the  soft  flesh  of  those  animals  which  annoy  the  Worm, 
since  the  sheath  does  not  penetrate  with  them  but  folds 
back,  it  follows  that  their  teeth  are  inserted  without  any 
protection,  and  that  on  account  of  their  backward  direction 


WORMS.  265 

they  can  be  withdrawn  only  with  great  difficulty  ;  thus,  in 
most  cases,  the  dart  becomes  broken ;  but  the  animal  is 
furnished  with  so  great  a  number,  that  these  losses  are 
scarcely  felt,  and  there  remain  to  it  amply  sufficient  for  its 
defence  in  all  contingencies."  * 

You  will  have  noticed  that  the  learned  French  zoologists 
seriously  countenance  the  notion  that  these  exquisitely 
elaborate  organs  are  weapons  of  offence.  But  in  this  I 
think  they  are  in  error,  misled  by  the  resemblance,  already 
alluded  to,  which  they  bear  to  weapons  of  human  construc- 
tion. The  manner  in  which  they  act  as  implements  of 
locomotion  has  been  beautifully  demonstrated  by  Dr.  Wil- 
liams in  the  Nereidous  Worms,  of  which  he  observes  that 
in  nearly  all  species  the  feet  are  constructed  with  express 
reference  to  progression  on  solid  surfaces.  In  many  in- 
stances, the  bristle  is  compound,  consisting  of  a  staff  with 
a  variously  armed  point  or  blade  jointed  to  its  extremity. 
"  Viewed  by  the  light  of  mechanical  principles,  nothing 
can  be  so  obvious  as  the  reason  why  the  seta  in  these,  as 
in  nearly  all  other  Annelida,  are  jointed.  If  they  con- 
sisted of  rigid,  unbending  levers,  it  is  manifest  that  they 
would  prove  most  awkward  additions  to  the  sides  of  the 
animals  ;  if  fixed  too  deeply  in  the  surrounding  soil,  they 
would  not  act  at  all  as  levers;  if  too  superficially,  the 
Worm  would  be  compressed  in  its  tube  at  the  moment 
when  the  seta  of  the  opposite  feet  would  meet  in  a  straight 
line.  These  difficulties  are  effectually  and  skilfully  ob- 
viated by  the  introduction  of  a  joint  or  a  point  of  motion 
on  each  seta.  This  is  one  instance  among  many  which 
the  eye  of  the  mechanician  would  detect  in  the  organisa- 
tion of  the  Annelida,  in  which  Nature  takes  adroit  ad- 
vantage of  mechanical  principles  in  the  attainment  of  her 
ends."  f 

Look  now,  in  illustration  of  these  principles,  at  the 
bristle-feet  of  this  beautiful  green  Phyllodoce.  No  doubt 
*  «  Litt.  de  la  France,"  ii.  71.  f  "  Rep.  on  Brit.  Annelida,"  211. 


266  EVENINGS    AT    THE    MICROSCOPE. 

you  have  often  seen  it  in  the  little  hollows  of  our  rocky 
ledges,  and  especially  on  beds  of  young  mussels  ;  and  pro- 
bably you  have  admired  the  elegant  ease  with  which  its 
lithe  and  tortuous  body  writhes  and  winds,  like  a  bit  of 
green  silken  cord,  in  and  out  among  the  compactly 
crowded  shells.  You  have  wondered,  too,  at  the  difficulty 
which  attends  the  attempt  to  take  it  up,  not  on  account  of 
the  rapidity  of  its  motions,  but  because  of  the  extreme 
slenderness  and  slipperiness  of  the  subject,  and  of  the 
power  which  it  possesses  of  insinuating  itself  into  the 
smallest  crevice. 

The  foot  in  this  genus  has  but  a  single  branch,  and  a 
single  pencil  of  bristles,  which  is  placed  between  the  flat 
swimming  leaf  that  ornaments  each  segment  and  the  lower 
cirrus.  The  bristles  are  of  the  compound  jointed  form, 
but  the  joint  is  fixed  in  a  peculiar  manner.  The  basal 
portion  is  drawn  out  into  a  very  slender  long  straight 
shaft,  terminating  in  a  knob  somewhat  resembling  the  end 
of  a  limb -bone.  This  is  slit  in  one  direction  to  receive  the 
terminal  piece,  which  is  shaped  somewhat  like  a  lance- 
head,  and  is  inserted  into  the  slit  exactly  as  a  knife-blade 
is  fixed  into  the  haft.  The  head  is  in  fact  a  knife-blade, 
with  a  thickened  back  and  a  very  thin  edge,  which  is 
notched  into  teeth  of  the  most  exquisite  delicacy.  The 
blade  is  slightly  curved,  and  drawn  out  into  a  long  acute 
point ;  and  the  whole  bristle  is  formed  out  of  an  elastic 
horny  substance  (probably  chitine),  that  rivals  in  transpa- 
rency and  brilliancy  the  purest  flint-glass. 

I  might  adduce  a  vast  variety  of  examples  of  these 
organs  in  the  Marine  Worms,  all  of  which  would  charm 
you  by  their  elegance  and  by  their  extreme  diversity  ;  but 
I  have  other  things  to  show  you  in  this  interesting  class  of 
animals,  which  fortunately  are  so  common  on  all  our 
shores  that  you  will  have  no  difficulty  in  procuring  plenty 
of  specimens  for  your  private  observation  and  study.  And 
if  you  need  intelligent  guidance  you  cannot  have  a  better 


WORMS.  267 

mentor  than  Dr.  Williams,  -whose  admirable  "  Report  on 
the  British  Annelida  "  I  have  just  cited. 

Before  we  dismiss  our  little  Phyllodoce  to  its  home  in 
the  aquarium,  we  must  try  to  get  a  sight  of  its  pretty 
mouth.  The  Worms  are  somewhat  wayward  in  displaying 
this  part  of  their  charms,  sometimes  exposing  it  at  in- 
tervals of  a  second  or  two  for  very  many  times  in  succes- 
sion, at  others  sullenly  keeping  it  closed ;  and  no  efforts 
that  I  am  aware  of  on  our  part  will  induce  the  display ; 
we  must  await  their  pleasure.  It  is,  in  fact,  a  turning  of 
the  throat  inside  out.  In  most  of  the  Worms  the  head  is 
minute  ;  and  what  seems  to  be  the  mouth  is  but  the  orifice 
from  which  the  throat  or  proboscis  is  everted.  In  the 
Phijllodoces  this  organ  is  a  great  muscular  sac,  hi  some 
species  equalling  in  length  one-fourth  of  the  whole  body. 

Ha !  there  it  appears !  What  a  chasm  yawns  in  the 
under  side  of  the  head,  as  the  interior  begins  rapidly  to 
protrude,  turning  inside  out  as  it  comes  forth,  like  a  living 
stocking,  until  it  assumes  the  form  of  an  enormous  (com- 
paratively enormous,  of  course,)  pear-shaped  bag,  the 
surface  of  which  is  beset  with  a  multitude  of  secreting 
warts  or  glands,  somewhat  like  the  papillae  which  stud  the 
tongue  in  higher  animals  !  The  extremity,  which  is  per- 
forated, is  surrounded  by  a  muscle,  by  means  of  which  it 
contracts  forcibly  on  whatever  it  is  applied  to,  and  thus 
holds  it  firmly,  while  the  re-inversion  of  the  sac  drags  it,  if 
suitable,  into  the  body  to  be  digested. 

But  this  huge  proboscis  disappears  as  rapidly  and  as 
wonderfully  as  it  was  revealed.  Commencing  at  what  is 
now  the  outer  extremity,  which  is  quickly  turned-in,  the 
whole  swiftly  returns  to  its  cavity  in  the  inverse  order  to 
that  in  which  it  was  extruded ;  and  now  that  it  is  all  en- 
gulphed,  we  marvel  that  so  vast  a  sac  can  be  packed  away 
in  so  slender  a  case. 

In  this  instance  the  armour  of  the  proboscis  is  feeble ; 
but  we  have  species  which  are  very  elaborately  armed. 


268  EVENINGS   AT    THE    MICEOSCOPE. 

There  is  a  minute  species  of  Lombrinereis,  which  commonly 
appears  in  our  aquaria  after  they  have  been  some  time 
established,  and  breeds  in  vast  numbers  on  the  floccose 
matter  that  clogs  the  bottom  and  sides.  In  this  tiny 
Worm  there  is  a  formidable  array  of  jaws,  resembling 
black  hooks,  which  we  may  discern  through  their  pellucid 
tissues,  snapping  and  cutting  viciously  like  so  many  pairs 
of  hooked  scissors.  Though  I  have  often  had  this  little 
species  in  my  tanks  in  copious  abundance,  I  regret  to  say 
I  cannot  find  any  at  this  moment  for  our  examination,  and 
shall  therefore  content  myself  with  translating  for  you 
MM.  Audouin  and  Milne-Edwards'  description  of  the  jaws, 
as  they  appear  in  a  closely-allied  form,  but  of  far  greater 
dimensions,  Eunice. 

"  The  proboscis  is  not  very  protrusile  ;  when  it  is  with- 
drawn its  external  orifice  is  longitudinal,  and  the  jaws  are 
fixed  on  each  side,  all  facing  the  medial  line.  When  it  is 
projected,  however,  the  two  margins  of  the  longitudinal 
cleft  become  transverse  in  separating,  and  the  jaws  follow 
the  same  movement,  and  diverge  in  the  ratio  of  their  for- 
wardness. A  kind  of  lower  lip  which  is  affixed  to  the 
under  side  of  the  proboscis  is  composed  of  two  horny 
blades  united  towards  their  front  extremity,  and  prolonged 
behind  into  points.  The  jaws  are  to  the  number  of  seven ; 
three  on  the  right  and  four  on  the  left ;  the  two  upper 
ones  are  perfectly  alike,  and  mutually  opposed ;  they  are 
large,  narrow,  pointed,  recurved  hook-wise  at  the  tip,  and 
jointed  at  their  hinder  ends  on  a  double  horny  stem 
shorter  than  themselves.  The  second  pair  of  jaws  are 
large,  broad  and  flat,  mutually  alike,  and  jointed  on  the 
lower  side  of  the  first  pair  ;  .  .  .  their  internal  edge  is 
straight  and  cut  into  deep  teeth.  The  third  pair  are 
small,  thin,  concave,  and  notched;  they  are  affixed  by 
their  inferior  edge  outside  and  in  front  of  the  second  pair, 
which  they  conceal  during  repose.  Finally,  the  super- 
numerary jaw  which  is  found  on  the  left  side  only,  is 


WORMS.  269 

small,  semicircular,  toothed,  and  placed  between  the  second 
and  third  pairs.  All  these  pieces  are  surpassed  by 
the  margin  of  the  proboscis,  which  is  often  hard  and 
black."  * 

From  this  complex  and  formidable  mouth  we  will  pass 
to  one  of  quite  another  form,  not  less  effective,  perhaps 
more  formidable,  but  ordained  by  the  goodness  of  God  to 
be  a  most  valuable  agent  in  the  relief  of  human  suffering. 
I  mean  the  medicinal  Leech,  of  which  we  can  readily  pro- 
cure a  specimen  from  our  friend  the  apothecary. 

Here  it  is.  There  is  no  protrusile  proboscis,  but  the 
throat  is  spacious,  and  capable  of  being  everted  to  a  slight 
degree.  The  front  border  of  the  mouth  is  enlarged  so  as 
to  form  a  sort  of  upper  lip,  and  this  combines  with  the 
wrinkled  muscular  margin  of  the  lower  and  lateral  portions 
to  form  the  sucker.  With  the  dissecting  scissors  I  slit 
down  the  ventral  margin  of  the  sucker,  exposing  the  whole 
throat.  Then  the  edges  being  folded  back,  we  see  im- 
planted in  the  walls  on  the  dorsal  region  of  the  cavity 
three  white  eminences  of  a  cartilaginous  texture,  which 
rise  to  a  sharp  crescent- 
shaped  edge ;  they  form 
a  triangular,  or  rather  a 
triradiate  figure. 

Now,  if  you  recollect, 
this  is  the  figure  of  the 
cut  made  in  the  flesh 
wherever  a  Leech  has 
sucked,  as  it  is  of  the 
scar  which  remains  after 

...      ,    ,   ,         THROAT  OF  LEECH  LAID  OPEN. 

the   wound   has   healed. 

For  these  three  little  eminences  are  the  implements  with 
which  the  animal,  impelled  by  its  blood- sucking  instincts, 
effects  its  purpose.  But  to  understand  the  action  more 
perfectly,  we  must  use  higher  powers. 

*  "  Litt.  de  la  France,"  ii.  138. 


'270  EVENINGS   AT    THE    MICROSCOPE. 

I  dissect  out  of  the  flesh,  then,  one  of  the  white  points, 
say  the  middle  one,  and  laying  it  in  water  in  the  compres- 
sorium,  flatten  the  drop,  but  use  no  more  pressure  than 
just  enough  for  that.  Now  I  apply  a  power  of  150  dia- 
meters, and  we  will  look  at  it  in  succession.  You  have 
under  your  eye  a  somewhat  pellucid  mass,  of  an  irregular 
oval  figure,  and  of  fibrous  texture,  one  side  of  which  is 
thinned  away  apparently  to  a  keen  edge  of  a  somewhat 
semicircular  outline.  But  along  this  edge,  and,  as  it  were, 
imbedded  into  it  for  about  one- third  of  their  length,  are 
set  between  seventy  and  eighty  crystalline  points,  of  highly 
refractive  substance,  resembling  glass.  These  points  gra- 
dually decrease  in  size  towards  one  end  of  the  series,  and 
at  length  cease,  leaving  a  portion  of  the  cutting  edge 
toothless.  At  the  end  where  they  are  largest  they  are 
nearly  close  together,  but  at  length  are  separated  by  spaces 
equal  to  their  own  thickness.  The  manner  in  which  they 
are  inserted  closely  resembles,  in  this  aspect,  the  insertion 
of  the  teeth  in  the  jaw  of  a  dolphin  or  crocodile. 

But  this  appearance  is  deceptive.  By  affixing  the  little 
jaw  to  the  revolving  needle,  we  bring  the  edge  to  face  our 
eye.  It  is  not  an  edge  at  all ;  but  a  narrow  parallel-sided 
margin  of  considerable  breadth.  And  the  teeth  are  not 
conical  points,  afe  they  seemed  when  we  viewed  them  side- 
wise,  but  flat  triangular 
plates,  with  a  deep  notch  in 
their  lower  edge.  Thus  they 
partly  embrace,  and  are 
partly  inserted  in,  the  mar- 
gin  of  the  jaw. 

Observe  now  how  beauti- 
fully this  apparatus  subserves 
the  purpose  for  which  it  is 
JAW  OF  LEECH  (in part}.  intended.     By  means  of  its 

sucker,  the  Leech  creates  a 
vacuum  upon  a  certain  part  of  the  skin,  exactly  like  that 


WORMS.  271 

produced  by  a  cupping-glass.  The  skin  covered  is  drawn 
into  the  hollow  so  far  as  to  render  it  quite  tight,  by  the 
pressure  of  the  surrounding  air.  Thus  it  is  brought  into 
contact  with  the  edges  of  the  three  jaws,  to  which,  by 
means  of  powerful  muscles  attached  to  them,  a  see-saw 
motion  is  communicated,  which  causes  the  little  teeth 
soon  to  cut  through  the  skin  and  superficial  vessels, 
from  which  the  blood  begins  to  flow.  The  issue  of  the 
vital  fluid  is  then  promoted  by  the  pressure  around,  and  so 
goes  on  until  the  enormous  stomach  of  the  Leech  is  dis- 
tended to  repletion. 

It  has  been  suggested  that  this  whole  contrivance,  with 
the  instinct  by  which  it  is  accompanied,  is  intended  for  the 
benefit  of  Man,  and  not  of  the  Leech.  Blood  seems  to  be 
by  no  means  the  natural  food  of  the  Leech  ;  it  has  been 
ascertained  to  remain  in  the  stomach  for  a  whole  twelve- 
month without  being  digested,  yet  remaining  fluid  and 
sound  during  the  entire  period :  while,  ordinarily,  such  a 
substance  cannot  in  one  instance  out  of  a  thousand  be 
swallowed  by  the  animal  in  a  state  of  nature.  Whether 
this  is  so  or  not, — whether  man's  relief  under  suffering 
was  the  sole  object  designed,  or  not,  it  was  certainly  one 
object ;  and  we  may  well  be  thankful  to  the  mercy  of  God, 
Who  has  ordained  comfort  through  so  strange  an  instru- 
mentality. 

The  progress  of  marine  natural  history,  as  studied  in 
the  aquarium,  has  made  our  drawing-rooms  and  halls 
familiar  with  a  multitude  of  curious  and  beautiful  creatures 
which  a  few  years  ago  were  -known  only,  and  that  very 
imperfectly,  to  the  learned  professors  of  technical  science. 
Among  the  forms  which  .embellish  our  tanks  are  several 
species  of  Serpula,  and  Worms  allied  to  it.  The  shelly 
contorted  tube  which  this  painted  Sea-worm  inhabits,  and 
which  it  has  built  up.  itself  around  its  own  body,  with  stone 
and  cement  which  that  body  supplied,  is  well  known  to 
you ;  as  is  also  the  curious  conical  stopper  with  which  it 


272  EVENINGS   AT    THE    MICBOSCOPE. 

closes  up  its  bottle  as  with  a  cork,  when  safe  at  home, 
and  the  lovely  crown  of  gorgeously  coloured  fans  which  it 
expands  when  it  takes  ("  the  air,"  I  was  about  to  say,  but 
rather)  the  water.  You  are  familiar,  too,  with  the  light- 
ning-like rapidity  with  which,  while  in  health  and  vigour, 
the  Serpulcij  on  the  slightest  alarm,  retreats  into  his  for- 
tress, taking  care  to  clap -to  the  door  after  him.  But 
perhaps  you  have  never  had  an  opportunity  of  examining 
the  mechanism  by  which  this  rapid  flight  is  effected. 

As  there  are  two  distinct  movements  performed  by  the 
Worm, — the  slow  and  cautious  and  gradual  protrusion, 
and  the  sudden  and  swift  retreat, — so  there  are  two  dis- 
tinct sets  of  organs  by  which  they  are  performed.  Shall  I 
sacrifice  one  from  this  fine  group  to  demonstrate  the 
mechanism  ?  "Well,  then,  I  carefully  break  the  shelly 
tube,  and  extract  the  worm  uninjured. 

Its  form  is,  you  perceive,  much  shorter  and  more 
dumpy  than  you  would  have  supposed  from  looking  at  the 
tube ;  and  it  is  somewhat  flattened,  having  a  back-  and  a 
belly-side.  On  the  former  there  is  a  sort  of  shield,  the 
sides  of  which  bear  wart-like  feet, — about  seven  pairs  in 
all} — which  are  perforated  for  the  working  of  protrusile 
pencils  of  bristles,  similar  in  structure  and  in  function  to 
those  which  we  lately  examined. 

Here  is  one  of  the  pencils  extracted.  To  the  naked  eye 
it  is  a  yellowish  body  with  a  satiny  lustre  ;  and  this  effect 
depends  upon  the  light  being  reflected  from  a  number  of 
nearly  parallel  lines, — the  staves  of  the  spear-like  bristles, 
— which  the  eye  cannot  resolve  in  detail.  A  drop  of  the 
caustic  solution  of  potash  cleanses  the  bundle  from  the 
fleshy  matter  which  would  otherwise  obscure  the  vision, 
and  now  I  place  it  on  the  stage. 

With  this  power  of  400  diameters  you  see  a  multitude 
— some  twenty  or  thirty,  or  more — of  very  long,  slender, 
straight  rods,  of  a  clear  yellowish  horny  substance,  set 
side  by  side,  like  a  sheaf  of  spears  in  an  armoury.  Each 


WORMS. 


273 


one  merges,  at  its  upper  end,  into  a  sort  of  blade,  which 
is  slightly  bent,  and  which  tapers  to  an  exceedingly  fine 
point.  But  its  chief  peculiarity  is  that  the  blade  has  a 
double  edge,  not  like  a  two-edged  sword,  the  edges  set  on 
opposite  faces,  but  on  the  same  face,  set  side  by  side, 
with  a  groove  between  them  ;  and  each  edge  is  cut  with 
the  most  delicate  and  close-set  teeth,  the  lines  of  which 
pass  back  upon  the  blade,  as  in  our  sickles. 


PrSHIJfG    FOLKS   OF   8ERPVLA. 


These  pencils  of  spear-like  bristles  are  the  organs  by 
which  the  protrusion  of  the  animal  is  performed.  Their 
action  is  manifestly  that  of  pushing  against  the  walls  of 
the  interior,  which  on  close  examination  are  seen  to  be 
lined  with  a  delicate  membrane,  exuded  from  the  animal's 
skin.  The  opposite  feet  of  one  segment  protrude  the  pen- 
cils of  bristles,  one  on  each  side,  the  acute  points  and 
teeth  of  which  penetrate  and  catch  in  the  lining  membrane ; 
the  segments  behind  this  are  now  drawn  up  close,  and  ex- 
tend their  bristles ;  these  catch  in  like  manner ;  then  an 
elongating  movement  takes  place  ;  the  pencils  of  the 
anterior  segments  being  now  retraced,  they  yield  to  the 
movement  and  are  pushed  forward,  while  the  others  are 
held  firm  by  the  resistance  of  their  holding  bristles ;  thus 
gradually  the  foreparts  of  the  animal  are  exposed. 

But  this  gradual  process  would  ill  suit  the  necessity  of  a 
creature  so  sensitive  to  alarm,  when  it  wishes  to  retreat. 
We  have  already  seen  how,  with  the  fleetness  of  a  thought, 
its  beautiful  crown  of  scarlet  plumes  disappears  within  its 

T 


274  EVENINGS   AT    THE   MICROSCOPE. 

stony  fastness  :    let  us  now  look  at  the  apparatus  which 
effects  this  movement. 

If  you  look  again  at  this  Serpula  recently  extracted,  you 
will  find,  with  a  lens,  a  pale  yellow  line  running  along  the 
upper  surface  of  each  foot,  transversely  to  the  length  of 
the  body.  This  is  the  border  of  an  exceedingly  delicate 
membrane ;  and  on  placing  it  under  a  higher  power  (say 
600  diameters)  you  will  be  astonished  at  the  elaborate 
provision  here  made  for  prehension.  This  yellow  line, 
which  cannot  be  perceived  by  the  unassisted  eye,  is  a 
muscular  ribbon,  over  which  stand  up  edgewise  a  multitude 
of  what  I  will  call  combs,  or  rather  sub-triangular  plates. 
These  have  a  wide  base ;  and  the  apex  of  the  triangle  is 
curved  over  into  an  abrupt  hook,  and  then  this  is  cut  into 
a  number  (from  four  to  six)  of  sharp  and  long  teeth.  The 
plates  stand  side  by  side,  parallel  to  each  other,  along  the 
whole  length  of  the  ribbon,  and  there  are  muscular  fibres 
seen  affixed  to  the  basal  side  of  each  plate,  which  doubtless 
give  it  independent  motion.  I  have  counted  136  plates 
on  one  ribbon  ;  there  are  two  ribbons  on  each  thoracic 
segment,  and  there  are  seven  such  segments ; — hence  we 
may  compute  the  total  number  of  prehensile  comb-like 


HOOKS    OF    SERPULA. 


plates  on  this  portion  of  the  body  to  be  about  one  thousand 
nine  hundred,  each  of  which  is  wielded  by  muscles  at  the 


WOEMS.  275 

will  of  the  animal ;  while,  as  each  plate  carries  on  an 
average  five  teeth,  there  are  nearly  ten  thousand  teeth 
hooked  into  the  lining  membrane  of  the  cell,  when  the 
animal  chooses  to  descend.  Even  this,  however,  is  very 
far  short  of  the  total  number,  because  long  ribbons  of 
hooks  of  a  similar  structure,  but  of  smaller  dimensions, 
run  across  the  abdominal  segments,  which  are  much  more 
numerous  than  the  thoracic.  No  wonder,  with  so  many 
muscles  wielding  so  many  grappling  hooks,  that  the  retreat 
is  so  rapidly  effected  1 


T2 


276  EVENINGS   AT    THE    MICROSCOPE. 


CHAPTER  XVI. 

SEA-URCHINS    AND     SEA-CUCUMBERS. 

PEERING  about  among  the  rocks  to-day  at  low-tide,  I 
found,  on  turning  over  a  large  stone,  an  object  which, 
though  familiar  enough  to  those  who  are  conversant  with 
the  sea  and  its  treasures,  would  surprise  a  curious  ob- 
server fresh  from  the  fields  of  Warwickshire.  It  is  a  ball, 
perfectly  circular,  and  nearly  globular, — -only  that  its  under 
part  is  a  little  flattened, — hard  and  shelly  in  its  exterior, 
which  is,  however,  densely  clothed  with  a  forest  of  shelly 
spines,  each  one  of  which  has  a  limited  amount  of  mobility 
on  its  own  base.  On  attempting  to  remove  it,  I  find  that  it 
adheres  to  the  stone  with  some  firmness  ;  and  that,  on  the 
exercise  of  sufficient  force,  it  comes  away  with  a  feeling  as 
if  something  were  torn,  and  I  find  that  a  multitude  of  little 
fleshy  points  are  left  on  the  stone.  Having  dropped  my 
prize  into  a  glass  collecting-jar  of  sea-water,  I  presently 
see  that  it  is  slowly  marching  up  the  side,  sprawling  out 
on  every  side  a  multitude  of  transparent  hands,  with  which 
it  seems  to  feel  its  way,  and  which  are  evidently  feet  also, 
for  on  these  it  crawls  along  at  its  own  tortoise-pace.  And 
I  now  see  that  it  is  the  knobbed  ends  of  some  of  these  feet 
which  were  torn  away  by  my  forcible  act  of  ejectment,  and 
left  clinging  to  the  stone. 

It  was  not  the  first  time  that  I  had  seen  the  Sea-urchin 
(Echinus  miliaris) ;  and  I  might  have  passed  it  by  with  a 
feeling  of  satiated  curiosity,  had  I  not  recollected  our 
evening's  amusement.  Oh,  ho  !  said  I,  what  a  fund  of 
microscopic  entertainment  is  inclosed  in  this  stone  box ! 


SEA-URCHINS   AND    SEA-CUCUMBERS.  277 

So  I  brought  it  home,  and  now  produce  it  as  the  text  of 
our  conversazione. 

Every  part  is  a  wonder ;  but  we  must  examine  each  in 
order.  Take  the  spines  first. 

As  we  examine  these  organs  on  the  animal  crawling  at 
ease  over  the  bottom  of  a  saucer  of  sea-water,  using  this 
triple  lens,  we  see  that  each  is  a  taper  pillar,  rounded  at 
the  summit,  and  swelling  at  the  base,  where  it  seems  to 
be  inserted  into  a  fleshy  pedestal,  on  which  it  freely 
moves,  bending  downward  in  all  directions,  and  describing 
a  circle  with  its  point,  of  which  the  base  is  the  centre. 
Each  spine  is  for  the  greater  portion  of  its  length  of  a 
delicate  pea-green  hue,  but  the  terminal  part  is  of  a  fine 
lilac  or  pale  purple.  The  whole  surface  appears  to  be 
fluted,  like  an  Ionic  column,  but  this  is  an  illusion,  as  you 
will  see  presently. 

I  now  detach  one  of  the  spines,  cutting  it  off  with  fine- 
pointed  scissors  as  near  the  base  as  I  can  reach.  I  put  it 
with  as  little  delay  as  possible  into  the  live-box,  and  exa- 
mine it  with  a  high  power,  say  600  diameters.  Look  at 
it.  You  see  the  ciliary  currents  very  distinctly;  and  if 
you  move  the  stage  so  as  to  bring  the  basal  portion  into 
view,  you  may  discern  even  the  cilia  themselves,  very 
numerous  and  short,  quivering  with  a  rapid  movement. 
The  currents  are  not  longitudinal,  but  transverse,  and 
somewhat  peculiar.  The  floating  atoms  which  come  within 
their  vortex  are  drawn  in  at  right  angles  to  the  axis  of  the 
spine,  and  are  presently  hurled  away  in  the  same  plane  ; 
forming  a  circle,  whose  plane  is  perpendicular  to  the  direc- 
tion of  the  spine.  The  surface  upon  which  these  cilia  are 
set  is  a  transparent  gelatinous  skin,  of  extreme  tenuity, 
stretched  tightly  over  the  solid  portion,  which  it  completely 
covers,  and  studded  with  minute  oval  orange-coloured 
grains. 

The  substance  of  which  the  spines  are  composed  is  best 
seen  by  crushing  a  few  of  these  organs  into  fragments. 


278  EVENINGS    AT    THE    MICROSCOPE. 

We  now  see  a  texture  beautifully  delicate  ;  they  are  formed 
of  calcareous  substance  as  transparent  as  glass,  and  re- 
flecting the  light  like  that  material ;  hard  but  very  brittle  ; 
clear  and  solid,  with  a  fibrous  appearance  in  some  parts, 
but  in  others  excavated  into  innumerable  smooth  rounded 
cavities  which  join  each  other  in  all  possible  ways.  It  is 
to  this  structure  that  the  spine  owes  its  strength,  its  light- 
ness, and  its  brittleness. 

This  arrangement  of  the  calcareous  deposit  in  a  sort  of 
glass  full  of  minute  inter- communicating  hollows  is  very 
peculiar,  but  it  is  invariably  found  in  the  solid  parts  of 
this  class  of  animals ;  so  that  the  experienced  naturalist, 
on  being  presented  with  the  minutest  fragment  of  solid 
substance,  would,  by  testing  it  with  his  microscope,  be 
able  at  once  to  affirm  with  certainty,  whether  it  had  be- 
longed to  an  Echinoderm  *  or  not.  And  this  uniformity 
obtains  in  all  the  diverse  forms  which  the  animals  assume, 
and  in  all  the  various  organs  which  are  strengthened  by 
calcareous  deposits — Crinoid,  Brittle-star,  Five-finger, 
Urchin,  Sea-gherkin,  or  Synapta;  ray,  plate,  spine, 
sucker-disk,  lantern,  pedicellaria,  dumb-bell,  wheel,  or 
skin-anchor, — whenever  we  find  calcareous  matter,  we 
invariably  find  it  honey-combed,  and  eroded,  as  it  were, 
in  this  remarkable  fashion. 

Dr.  Carpenter  has  described  this  texture  so  well,  that  I 
shall  not  apologise  for  quoting  his  words  to  you,  especially 
as  you  will  have  an  opportunity  here  of  testing  their  cor- 
rectness, by  personal  observation.  "  It  is,"  he  remarks, 
"  in  the  structure  of  that  calcareous  skeleton,  which  pro- 
bably exists,  under  some  form  or  other,  in  every  member 
of  this  class,  that  the  microscopist  finds  most  to  interest 
him.  This  attains  its  highest  development  in  the  Echinida, 
in  which  it  forms  a  box- like  shell,  or  « test,'  composed  of 

*  From  the  Greek  ex^os  (echinos)  a  hedgehog,  and  Sepua  (derma)  skin. 
A  name  given  to  these  animals  from  their  bodies  being  generally  armed 
with  spines. 


SEA-URCHINS   AND    SEA-CUCUMBERS.  279 

numerous  polygonal  plates  joined  to  each  other  with  great 
exactness,  and  beset  on  its  external  surface  with  *  spines,' 
which  may  have  the  form  of  prickles  of  no  great  length, 
or  may  be  stout,  club-shaped  bodies,  or,  again,  may  be 
very  long  and  slender  rods.  The  intimate  structure  of  the 
shell  is  everywhere  the  same  :  for  it  is  composed  of  a  net- 
work, which  consists  of  carbonate  of  lime,  with  a  very 
small  quantity  of  animal  matter  as  a  basis,  and  which 
extends  in  every  direction  (i.e.,  in  thickness,  as  well  as  in 
length  and  breadth),  its  areolse  or  interspaces  freely  com- 
municating with  each  other.  These  '  areolse,'  and  the 
solid  structure  which  surrounds  them,  may  bear  an  ex- 
tremely variable  proportion  one  to  the  other ;  so  that,  in 
two  masses  of  equal  size,  the  one  or  the  other  may  greatly 
predominate  ;  and  the  texture  may  have  either  a  remark- 
able lightness  and  porosity,  if  the  network  be  a  very  open 
one,  or  may  possess  a  considerable  degree  of  compactness 
if  the  solid  portion  be  strengthened.  Generally  speaking, 
the  different  layers  of  this  network,  which  are  connected 
together  by  pillars  that  pass  from  one  to  the  other  in  a 
direction  perpendicular  to  their  plane,  are  so  arranged  that 
the  perforations  in  one  shall  correspond  to  the  intermediate 
solid  structure  in  the  next ;  and  their  transparency  is  such, 
that  when  we  are  examining  a  section  thin  enough  to  con- 
tain two  or  three  such  layers,  it  is  easy,  by  properly 
4  focussing '  the  microscope,  to  bring  any  one  of  them 
into  distinct  view.  From  this  very  simple  but  very  beau- 
tiful arrangement,  it  comes  to  pass  that  the  plates  of 
which  the  entire  '  test '  is  made  up,  possess  a  very  con- 
siderable degree  of  strength ;  notwithstanding  that  their 
porousness  is  such,  that  if  a  portion  of  a  fractured  edge, 
or  any  other  part  from  which  the  investing  membrane  has 
been  removed,  be  laid  upon  fluid  of  almost  any  description, 
this  will  be  rapidly  sucked  up  into  its  substance."  * 

To  return,  however,  to  our  spine.     When  we  look  at  it 
*  "  The  Microscope,"  553. 


280  EVENINGS   AT    THE    MICROSCOPE. 

laterally,  the  appearance  is  such  that  we  cannot  but  firmly 
believe,  that  it  is  grooved  throughout  with  straight  and 
deep  longitudinal  furrows.  But  if  we  break  off  the  same 
spine  transversely,  and  so  exhibit  it  that  the  broken  end 
shall  be  presented  to  the  eye,  we  perceive  that  there  are 
no  grooves ;  but  that  the  points  in  the  circumference, 
which  seemed  to  be  the  summits  of  the  ridges,  which  are 
very  narrow,  are  really  lower  than  the  intermediate  spaces, 
which  we  supposed  to  be  the  grooves,  and  that  the  surface 
of  these  spaces  is  really  convex  in  a  slight  degree. 

The  explanation  of  these  contradictory  appearances  is 
easily  given.  Meanwhile,  however,  they  read  an  important 
lesson  to  the  inexperienced  microscopist,  not  to  decide  too 
hastily  on  the  character  of  a  surface  or  a  structure,  from 
one  aspect  merely.  So  many  are  the  chances  of  illusion, 
that  the  student  should  always  seek  to  view  his  subject  in 
different  aspects,  and  under  varying  conditions  of  light, 
position,  &c. 

It  is  by  making  a  thin  transverse  section  of  a  spine, — 
cutting  off  a  slice  of  it,  to  speak  in  homely  phrase, — that 
we  shall  demonstrate  the  structure,  which  is  very  beau- 
tiful. This  is  an  operation  requiring  much  delicacy  and 
practice,  and  implements  for  the  special  purpose ;  and 
hence  it  is  best  performed  by  professional  persons,  who 
prepare  microscopic  objects  for  sale.  You  may  see  such  a 
section,  however,  on  this  slide  ;  but  I  do  not  know  whether 
the  spine  belongs  to  the  species  we  are  examining. 

The  whole  central  portion  is  formed  of  the  sponge-like 
calcareous  matter,  which,  from  the  variously  reflected  and 
refracted  rays  of  light,  appears  nearly  opaque,  and  of  a 
bluish  colour  by  transmitted  light.  This  structure  sends 
forth  radiating  points  (making  longitudinal  ridges,  of 
course,  in  the  perfect  spine) ;  and  it  is  the  opacity  of  these 
points  (or  ridges)  which  reach  the  circumference,  that 
gives  to  the  spine  the  appearance  of  being  fluted.  Indeed 
it  would  be  fluted  if  this  were  the  entire  structure  ;  but  the 


SEA-UBCHINS    AND    SEA- CUCUMBERS.  281 

open  space  left  between  these  projecting  radii  is  filled  with 
the  solid  glassy  matter,  having,  as  we  see,  a  convex  sur- 
face. This,  however,  from  its  perfect  transparency,  is  not 
seen  when  we  look  at  the  side  of  the  spine,  the  eye  going 
down  through  the  transparent  matter  to  the  bottom  of  the 
space.  The  spine  is,  in  fact,  a  fluted  column  of  spongy 
glass,  with  the  grooves  filled  with  solid  glass. 

We  have  not  yet  seen,  however,  the  beautiful  mechanism 
appropriated  to  the  movement  of  these  spines.  You  can 
hardly  see  this  to  advantage  in 
the  living  animal,  but  here  is 
the  entire  shelly  box  of  a  dead 
Echinus,  on  which,  while  for 
the  most  part  the  surface  is 
denuded  of  spines,  a  few  dozen 
remain  sufficiently  attached  to 
show  what  I  wish  to  demon- 
strate, viz.,  the  mode  of  articu- 
lation. You  observe  that  the 
whole  globose  shell  is  covered 
with  tiny  knobs,  differing  in 
size,  and  not  set  in  very  re- 
gular, or  at  least  not  very  ob- 
vious, order,  but  showing  a  •"**  OP  KCHINTTS. 
tendency  to  run  in  lines  from 

pole  to  pole  of  the  globe.  Giving  attention  to  one  of  the 
larger  of  these  knobs,  under  a  lens  it  is  seen  to  be  a  hemi- 
spherical eminence  on  the  shell,  the  very  summit  of  which 
is  crowned  by  a  tiny  nipple  of  polished  whiteness,  resem- 
bling ivory.  Now  if  we  carefully  lift  one  of  the  still 
remaining  spines  from  its  attachment,  which  in  its  present 
dried  state  is  so  fragile  that  the  slightest  touch  is  sufficient 
for  the  purpose,  we  shall  note  that  its  base  rests  on  this 
tiny  nipple  ;  and  on  turning  it  up,  and  bringing  the  mag- 
nifying power  to  bear  upon  its  base,  we  see  that  this  is 
excavated  with  a  hollow,  whose  dimensions  exactly  corre- 


282  EVENINGS    AT    THE    MICROSCOPE. 

spond  with  those  of  the  nipple.  It  is  indeed  a  true  "  ball 
and  socket "  joint,  like  that  of  the  human  hip  or  shoulder, 
and  is  surrounded  by  a  capsular  ligament  to  keep  it  in 
place,  the  muscles  which  sway  the  spine  from  side  to  side 
and  cause  it  to  rotate  being  inserted  outside  the  capsule  or 
case.  Professor  Edward  Forbes  calculates  that  upon  a 
large  Echinus,  such  as  this  dried  specimen  of  E.  sphara, 
there  are  more  than  four  thousand  spines,  every  one  of 
which  has  the  structure,  the  mechanism,  and  the  move- 
ments that  we  have  been  examining.  Well  may  he  say, 
that  "  truly  the  skill  of  the  Great  Architect  of  Nature  is 
not  less  displayed  in  the  construction  of  a  Sea-urchin  than 
in  the  building  up  of  a  world  !  " 

To  return  now  to  our  little  E.  miliaris,  which  has  been 
all  this  time  coursing  round  and  round  his  saucer,  wonder- 
ing, perchance,  at  the  narrowness  and  shallowness  of  the 
White  Sea  in  which  he  finds  himself.  Again  we  peer,  lens 
to  eye,  over  the  bristling  surface,  and  discern,  shooting  up 
amidst  the  spines,  and  almost  as  thickly  crowded  as  they, 
multitudes  of  the  tiny  organs  which  have  caused  so  much 
doubt  and  discussion  among  naturalists.  Miiller,  the  great 
marine  zoologist  of  Denmark,  who  first  discovered  them, 
thought  them  parasitic  animals,  living  piratically  upon  the 
unwilling  Urchin,  and  accordingly  gave  them  generic  and 
specific  names.  The  term  pedicellaria,  which  he  assigned 
to  his  supposed  genus,  is  that  by  which  modern  natu- 
ralists have  agreed  to  call  them  still,  though  the  word  is 
not  now  used  in  a  generic  sense,  since  it  is  indubitably 
established  that  they  are  not  independent  animals,  but 
essential  parts  of  the  Urchin  itself.  Miiller  described 
three  distinct  sorts,  and  I  have  added  a  fourth  to  the 
number;  they  are  named  P.  triphyUa,  tridens,  globifei-a, 
and  stereophylla.  They  all  agree  in  these  particulars : — 
that  each  has  a  long,  slender,  cylindrical,  fleshy  stem, 
through  the  centre  of  which  runs  an  axis  or  rod  of  calca- 
reous substance ;  that  the  base  of  the  stem  rests  on  the 


SEA-URCHINS   AND    SEA-CUCUMBERS.  283 

skin  of  the  Urchin  ;  that  on  the  summit  is  placed  a  head 
consisting  of  three  pieces,  which  are  capable  of  being 
widely  opened  and  of  being  closed  together,  at  least  at 
their  tips  ;  that  the  edges  of  these  pieces,  which  come  into 
mutual  contact,  are  furnished  with  teeth,  which  lock  into 
each  other  ;  that  the  head-pieces  (like  the  stem)  consist  of 
calcareous  centres,  clothed  with  flesh ;  that,  besides  the 
opening  and  shutting  of  the  head,  the  stem  can  be  swayed 
from  side  to  side  ;  and  that  all  these  movements  are  spon- 
taneous, and  apparently  voluntary.  It  appears  that  the 
head-pieces  close  on  any  object  presented  to  them,  such  as 
the  point  of  a  needle,  and  hold  with  considerable  force  and 
tenacity,  so  that  the  pedicellaria  may  be  drawn  out  of  the 
water  without  relaxing  its  grasp. 

Looking  at  one  of  the  first-named  kind,  the  pedicellaria 
triphylla,  of  this  Echinus  miliaris,  we  see  that  it  consists 
of  three  broad  and  thick  somewhat  triangular  pieces, 
jointed  into  a  head,  set  on  a  thickish  stem  of  transparent 
gelatinous  fibrous  substance,  through  which  a  slender  core 
of  calcareous  matter  runs  that  looks  fibrous  and  blue. 
The  three  movable  pieces  or  blades  are  convex  externally, 
concave  internally ;  thin  in  substance,  furnished  along 
their  opposite  or  concave  sides  with  two  longitudinal  ridges 
or  keels,  each  of  which  is  cut  into  the  most  beautifully  fine 
teeth,  so  that  the  edge  of  each  ridge  looks  like  a  shark's 
tooth ;  the  edges  of  the  pieces  are  also  similarly  toothed  : 
these  shut  precisely  into  each  other. 

In  the  larger  E.  sphara,  the  head-blades  of  this  kind 
have  one  stout  central  ridge,  which  is  rounded  and  not 
toothed.  It  forms  the  front  of  a  great  interior  cavity 
which  opens  by  two  orifices  on  each  side  of  the  column. 

The  movable  pieces  inclose  a  skeleton  of  calcareous 
substance,  glassy,  colourless,  and  brittle,  in  which,  accord- 
ing to  the  plan  I  have  already  described,  are  excavated  a 
multitude  of  oval  cavities  which  form  irregular  rows ;  a 
central  line  runs  down  each  piece,  that  is  solid  and  free 


284  EVENINGS   AT    THE   MICROSCOPE. 

from  cavities.  This  calcareous  skeleton  is  encased  in  a 
gelatinous  flesh,  similar  to  and  continuous  with  that  of  the 
stalk. 

This  is  the  smallest  kind,  the  head  being  about  3yh  of 
an  inch  in  height. 

Considerable  modifications  are  found  to  exist  in  the  de- 
tails of  each  form,  in  the  relative  proportions  which  the 
parts  bear  to  each  other,  and  so  forth  ;  so  that  two  forms, 
which  in  their  extreme  conditions  widely  differ,  mutually 
approach,  and  appear  to  run  into  each  other.  This  is  the 
case  with  the  present,  and  with  the  form  which  I  will  now 
show  you. 

P.  tridens  is  much  larger  than  any  of  the  other  forms, 
the  movable  head  being  about  ^th 
of  an  inch  in  length,  and  the  whole 
organ  about  £th  of  an  inch.  This 
may  be  considered  as  essentially 
P.  triphylla,  modified  by  the 
blades  being  greatly  drawn  out  in 
length,  and  at  the  same  time  ren- 
dered quite  slender,  so  that  they  may 
be  called  pins ;  they  meet  only  at 
the  points,  where  they  often  cross 
the  spaces  between  the  basal  parts 
being  open.  The  inner  edges  of 
these  are  notched  with  teeth  as  in 
P.  triphylla,  of  which  those  near 
the  tips  are  larger  and  cut  into  sub- 
ordinate teeth  of  exquisite  minute  - 


We  have  here  an  opportunity  of 
seeing  that  the  oval  or  square  mark- 
™Z8> which  ™G  thickly  placed  through- 
out  the  calcareous  substance  of  the 
blades,  are  certainly  cavities  in  it ;  for  in  those  examples 
in  which  the  pins,  which  are  very  brittle,  are  broken,  the 


SEA-UECHINS   AND    SEA-CUCUMBEBS.  285 

edge  of  the  fracture  is  not  even,  but  jagged  with  holes  ex- 
actly corresponding  with  the  marks  in  question ;  so  that 
the  structure  is  the  same  as  that  of  the  spines  and  of  all 
the  other  solid  parts  of  the  Urchin. 

We  will  now  examine  some  specimens  of  P.  tridens, 
treated  with  potash,  which  will  enable  us  to  see  the  calca- 
reous support  better.  The  head-blades  expand  at  the  base 
into  three-sided  figures,  each  of  the  two  interior  sides  of 
which  is  indented  with  a  large  cavity,  leaving  a  projecting 
dividing  ridge,  armed  with  teeth  somewhat  remote  from 
each  other.  The  one  exterior  angle  is  toothed  in  a  cor- 
responding manner,  but  the  opposite  angle  appears  plain. 
The  angle  of  one  blade-base  fits  into  the  cavity  of  its 
neighbour ;  and,  so  far  as  I  have  observed,  when  the  two 
edges  thus  overlap,  it  is  the  toothed  one  that  is  on  the  out- 
side. Looking  from  the  circumference  towards  the  centre 
of  the  head,  it  is  the  left  angle  that  is  toothed  and  external, 
the  right  being  plain  and  sheathed.  This  observation, 
however,  applies  only  to  E.  miliaris;  for,  in  the  corre- 
sponding organs  of  E.  spharra,  both  sides  of  the  three- 
cornered  base  appear  untoothed,  except  close  to  the 
bottom,  where  a  deep  notch  indents  each  margin. 

Viewed  from  beneath,  the  head  assumes  an  outline 
which  is  rondo -triangular ;  but  yet  such  that  each  side  of 
the  triangle  has  a  very  obtuse  projecting  angle  in  the 
middle,  where  the  blade-bases  meet  each  other.  They  fit 
accurately,  and  each  has  a  deep  oblong  cavity  in  its 
bottom,  which  does  not,  as  I  conceive,  communicate  with 
the  interior. 

By  selecting  one  of  these  heads,  which  has  been 
divested  of  its  fleshy  parts  by  immersion  in  caustic  pot- 
ash, and  then  well  cleansed  by  soaking  in  clean  water, 
and  placing  it  under  a  low  power  of  the  microscope — 
100  diameters,  for  example — with  a  dark  ground,  and  the 
light  of  the  lamp  cast  strongly  upon  it  by  means  of  the 
Ldeberkuhn,  or  the  side-condenser,  we  shall  have  an  object 


EVENINGS   AT    THE    MICROSCOPE. 

of  most  exquisite  beauty.  The  material  has  all  the  trans- 
parency and  sparkling  brilliance  of  flint-glass,  while  the 
elegantly-shaped  pins,  the  perfect  symmetry  of  the  bases, 
the  arch  which  is  lightly  thrown  across  their  cavity,  the 
minute  teeth  of  the  tips  locking  accurately  into  each  other, 
and  the  oval  cavities  in  the  whole  structure  set  in  regular 
rows,  and  reflecting  the  light  from  thousands  of  points, 
constitute  a  spectacle  which  cannot  fail  to  elicit  your 
admiration. 

P.  globifera  is  formed  on  the  same  model  as  P.  triphylla, 
but  is  more  globose,  and  each  piece  appears  to  have  a 
deep  cleft  at  the  point,  which  does  not  extend  to  the  inte- 
rior side,  where  a  thick  ridge  runs  down  from  the  point  to 
the  base.  At  the  summit  of  this  ridge,  in  each  of  the  three 
divisions,  there  is  set  a  strong  acute  spine,  directly  hori- 
zontally inwards,  so  that  the  three  cross  each  other  when 
the  blades  close,  which  they  do  energetically, — a  formida- 
ble apparatus  of  prehension  !  The  stem  is  much  more 
slender  than  in  P.  triphylla,  and  the  height  of  the  head  of 
one  of  average  size  is  only  ^7rd  of  an  inch.  It  is  peculiar 
also  in  being  slender  throughout,  and  in  having  the  knobbed 
calcareous  stalk  extending  up  to  the  head,  which  appears 
to  work  on  it.  In  each  of  the  other  sorts  the  stalk  extends 
only  through  a  part  of  the  distance,  above  which  the  in- 
vesting fleshy  neck  becomes  wider  and  empty. 

But  the  internal  structure  is  not  quite  the  same  as  in 
the  others.  The  main  portion  of  the  head  is  composed  of 
gelatinous  flesh ;  the  calcareous  support  being  reduced  to 
that  ridge  which  runs  up  the  interior  side  of  the  blade. 
This  is  somewhat  bottle-shaped,  with  a  bulbous  base,  and  a 
long  slender  neck,  with  two  edges  on  the  inner  face,  which 
are  armed  with  horizontal  hooked  spines,  some  of  which  are 
double ;  and  the  whole  terminates  in  a  sort  of  ring,  formed 
by  the  last  pair  of  spines,  which  unite  into  the  acute  hori- 
zontal point  that  I  have  already  mentioned.  The  skeleton 
is  filled  with  oval  cavities,  like  that  of  the  others. 


SEA-UECHINS    AND    SEA-CUCUMBEBS.  287 

The  fourth  kind  of  Pedicellaria,  which  I  call  P.  stereo- 
pliylla,  is  quite  distinct  from  any  of  the  others.  It  is 
very  minute,  the  head  being  only  ^J-^th  of  an  inch  in 
height.  The  head  is  a  kind  of  lengthened  sphere,  cut  into 
three  segments,  exactly  as  if  an  orange  were  divided  by 
three  perpendicular  incisions,  meeting  at  the  centre.  Thus 
the  blades  meet  accurately  in  every  part  when  closed,  but 
expand  to  a  horizontal  condition.  These  are  almost 
entirely  calcareous,  being  invested  but  thinly  with  the 
gelatinous  flesh.  They  are  filled  with  the  usual  oval  cavi- 
ties, set  in  arched  rows. 

The  head  is  set  on  a  hollow  gelatinous  neck  nearly  as 
wide  as  itself,  and  thrown  into  numerous  annular  wrinkles ; 
its  walls  are  comparatively  thin,  disclosing  a  wide  cavity, 
apparently  quite  empty,  as  the  blue  calcareous  stem  ex- 
tends only  half-way  from  the  base  to  the  head.  At  this 
point  the  neck  contracts  rather  abruptly,  and  continues  to 
the  base,  but  just  wide  enough  to  invest  the  stem. 

This  sort  is  confined,  so  far  as  I  have  seen,  to  the 
ovarian  plates  and  their  vicinity,  where  they  are  numer- 
ous. 

Thus  these  tiny  organs,  so  totally  unlike  anything  with 
which  we  may  parallel  them  in  other  classes  of  animals, 
do  not  merely  afford  us  amusement,  and  delight  us  by  their 
elegance  of  shape  and  sparkling  beauty,  the  variety  and 
singularity  of  their  forms,  the  elaborateness  of  their  struc- 
ture, and  the  perfection  of  their  mechanism,  but  excite  our 
marvel  as  to  what  can  be  the  object  which  they  subserve  in 
the  economy  of  the  creature,— -.-what  purpose  can  be  fulfilled 
by  so  many  hundreds  of  organs  so  singular  and  scattered 
over  the  whole  surface  of  the  shelly  body. 

It  is  very  difficult  to  answer  this  question.  The  only 
organs  with  which  they  can  be  compared  are  the  singular 
"birds'  heads"  in  so  many  of  the  Polyzoa,  which  we 
looked  at  some  time  ago.  But,  unfortunately,  a  like  mys- 
tery enshrouds  the  use  of  those  processes,  and  the  only 


288  EVENINGS    AT    THE    MICROSCOPE. 

light  that  we  have  as  yet  upon  either  form  is  that  of  dim 
conjecture.  It  has  been  supposed  that,  in  both  cases,  the 
function  of  the  prehensile  forceps  is  to  seize  minute  animal- 
cules or  floating  atoms  of  food,  and  pass  them  to  the 
mouth:  but  the  supposition  is  involved  in  great  diffi- 
culties ;  as  the  organs,  however  fitted  for  prehension,  seem 
peculiarly  unsuited  for  transmitting  objects ;  besides  that 
the  great  majority  of  them  are  placed  very  remote  from  the 
mouth.  I  can  only  repeat  the  conjecture  which  I  hazarded 
in  the  case  of  the  Polyzoan  "  birds'  heads,"  viz.,  that  the 
pedicellaria  are  intended  to  seize  minute  animals,  and  to 
hold  them  till  they  die  and  decompose,  as  baits  to  attract 
clouds  of  Infusoria,  which,  multiplying  in  the  vicinity  of 
the  Urchin,  may  afford  it  an  abundant  supply  of  food. 

There  is  yet  another  series  of  organs  which  stretch  out 
from  every  part  of  the  surface  of  this  living  box ;  scarcely 
less  numerous  than  either  the  spines  or  pedicellarice,  but 
very  different  from  both.  They  are  what  I  alluded  to  just 
now  as  the  feet.  Let  us  pay  a  moment's  attention  to  their 
appearance  and  action,  before  we  examine  their  structure. 

We  see,  then,  extending  from  various  points  of  the 
shelly  case  of  the  Urchin,  and  reaching  to  twice  or  thrice 
the  length  of  the  longest  spines,  slender  pellucid  tubes, 
slightly  tapering  towards  their  free  extremity,  which  then 
abruptly  dilates  into  a  hemispherical  knob,  with  a  flat  end. 
These  very  delicate  organs  are  extended  or  contracted  at 
the  will  of  the  animal,  and  turned  in  every  direction, 
waved  hither  and  thither,  and  evidently  have  the  faculty 
of  adhering  very  firmly  by  their  dilated  tips  to  any  object 
to  which  they  are  applied. 

So  much  we  can  discern  as  we  watch  the  creature  dis- 
porting in  this  vessel  of  water ;  but  we  will  now  endeavour 
to  learn  a  little  more  about  its  structure  and  economy. 
Selecting  for  this  purpose  a  sucker  which  is  extended  to 
great  length,  I  snip  it  across  with  a  pair  of  sharp  scissors, 
as  near  the  base  as  I  can.  Mark  the  result.  The  terminal 


SEA-URCHINS    AND    SEA-CUCUMBERS. 


289 


SVCKEE   OF   URCHIX. 


knob  which  was  attached  to  the  bottom  of  the  saucer 
maintains  its  hold,  but  the  tube  has  suddenly  shrunk  up 
to  a  sixth  part  of  its 
former  length,  ex- 
changing at  the  same 
time  its  smooth  slen- 
derness  and  translu- 
.cency  for  a  wrinkled 
semi-opacity.  I  push 
the  knob  aside  with  a 
needle's  point  and  thus 
destroy  its  adhesion ; 
which  done,  I  take 
up  the  severed  and 
shrunken  sucker,  and  lay  it  in  a  little  sea-water  in  the 
live-box. 

Under  a  power  of  180  diameters  we  see  that  the  tube  is 
composed  of  two  series  of  muscular  fibres,  the  one  set 
running  lengthwise,  the  other  transversely  or  in  rings ; 
the  former  by  their  contraction  diminishing  the  length  of 
the  tube,  the  latter  diminishing  its  calibre.  The  muscular 
walls  are  covered  with  a  transparent  skin,  studded  with 
round  orange-coloured  spots,  perhaps  glandular,  exactly 
similar  to  those  we  saw  on  the  exterior  of  the  spines  and 
pedicellaria. 

Now,  to  illustrate  the  action 
of  these  tubular  feet,  I  must 
again  have  recourse  to  the  de- 
nuded shell  of  a  preserved 
Echinus.  Taking  this  globose 
empty  box  in  your  hand,  hold 
it  up  against  the  light,  look- 
ing in  at  the  large  orifice,  which 
was  once  occupied  by  the 
mouth :  —  you  see  that  the 
whole  shell  is  pierced  with 

u 


PORES  OP  UECHIX. 


290  EVENINGS   AT    THE   MICROSCOPE. 

minute  holes  or  pores,  which  are  arranged  in  ten  longitudi- 
nal lines,  associated  so  as  to  make  five  pairs  of  lines. 
Now  with  a  lens  examine  more  minutely  a  portion  of  any 
one  of  these  lines,  and  you  discern  that  it  is  composed  of 
a  multitude  of  pores,  which  have  a  peculiar  order  of  ar^ 
rangement  among  themselves ;  that  is  to  say,  they  form 
minor  rows  which  cross,  obliquely  or  diagonally,  the  course 
of  the  longitudinal  line.  These  rows  are  themselves  double, 
the  pores  running  in  pairs,  not  however  with  mathematical 
symmetry.  In  this  species,  there  are  three  pairs  of  pores 
in  each  row,  and  so  there  are  in  the  one  which  I  have 
here  alive,  but  in  other  of  our  native  species  the  rows  con- 
sist of  five  pairs. 

These  pores  are  intimately  connected  with  the  tubular 
feet,  each  of  which  springs  from  a  portion  of  the  shell  that 
is  perforated  with  a  pair  of  pores  ;  so  that  the  cavity  of 
every  tube  communicates  with  the  interior  of  the  shelly 
box  by  two  orifices. 

Now,  on  the  interior  side  of  these  two  pores, — that  is, 
within  the  cavity  of  the  shell, — there  is  placed  a  little 
membranous,  or  rather  muscular,  bladder,  filled  with  a 
fluid  which  is  not  materially  different  from  sea-water. 
There  is  a  free  communication  between  the  bladder  within 
and  the  tube  without  the  shell,  by  means  of  the  pair  of 
pores,  through  which  the  fluid  passes.  By  means  of  the 
muscular  fibres,  which  are  under  the  control  of  the 
Urchin's  will,  any  portion  of  this  double  vessel  can  be 
contracted  to  a  certain  extent.  Suppose  it  is  the  interior 
bladder ;  the  effect  of  the  contraction  of  its  walls  is  to 
diminish  its  capacity,  and  the  contained  fluid  is  forced 
through  the  pores  into  the  tube  without.  The  longitudinal 
fibres  of  this  part  being  at  the  same  moment  relaxed,  the 
tube  is  lengthened,  because  of  the  injected  water.  Sup- 
pose, now,  in  turn,  the  fibres  of  the  tube  contract,  while 
those  of  the  bladder  relax;  the  fluid  is  driven  back,  the 
bladder  dilates,  and  the  tube  shortens,  until,  if  the  animal 


SEA-URCHINS  AND   SEA-CUCUMBEBS.  291 

so  please,  its  swollen  tip  is  brought  close  up  to  the  pores. 
By  mechanism  so  beautiful  and  simple  is  the  prolongation 
or  abbreviation  of  these  organs  effected. 

We  noticed,  however,  that  the  extremities  of  the  tubes 
had  an  adhesive  power,  which  faculty  it  is  that  constitutes 
them  feet.  They  are  prehensile,  and  thus  they  afford,  as 
we  observed  in  the  living  Urchin,  the  means  by  which  it 
takes  hold  of  even  a  smooth  and  vertical  surface,  as  the 
side  of  a  glass  tank,  and  drags  up  its  body  thereby. 

Putting,  now,  the  extremity  of  this  cut-off  tube  under 
graduated  pressure,  having  first  applied  to  it  a  drop  of 
caustic  potash,  we  see  that  it  carries  a  beautiful  glassy 
plate  of  extreme  thinness,  which  lies  free  in  the  swollen 
cavity  of  the  termination  of  the  tube.  This  plate  is  cir- 
cular in  form,  apparently  notched  at  the  margin,  and  cut 
with  four  or  five  (for  the  number  varies)  incisions,  which 
reach  almost  to  the  centre.  The  substance  is  formed  of 
the  common  clear  brittle  calcareous  matter  of  the  skeleton, 
hollowed  into  numberless  cavities,  according  to  the  general 
plan.  The  centre  is  perforated  with  a  larger  round  orifice. 
The  appearance  of  marginal  notching  is  deceptive  ;  and  in-  . 
dicates  a  structure  analogous  to  what  we  see  in  the  spine. 
The  notched  line  indicates  the  extent  of  the  spongy  struc- 
ture ;  but  beyond  this  the  plate  extends  into  a  perfectly 
circular  smooth  edge,  but  is  constituted  of  a  layer  of  calca- 
reous substance  so  thin  that  there  is  no  room  for  the 
ordinary  cavities  within  it. 

The  round  aperture  in  the  centre  plays  an  important 
part  in  the  function  of  the  organ.  The  foot  adheres  on 
the  same  principle  as  that  by  which  children  take  up  large 
flat  stones  with  a  piece  of  wetted  leather,  to  the  middle  of 
which  a  string  is  attached.  The  boy  drops  his  sucker  on 
the  stone,  and  treads  firmly  on  it,  to  bring  it  into  close 
contact  with  the  surface  ;  then  he  pulls  at  the  string  per- 
pendicularly, by  which  the  central  part  of  the  leather  is 
lifted  a  little  way  from  the  stone,  leaving  a  vacuum  there ; 


292  EVENINGS   AT    THE    MICROSCOPE. 

since  the  contact  of  the  edges  with  the  stone  is  so  perfect 
that  no  air  can  find  entrance  between  them.  Now  the 
pressure  of  the  atmosphere  upon 
the  leather  is  so  great  that  a  con- 
siderable weight,  perhaps  half-a- 
dozen  pounds,  may  be  lifted  by 
the  string  before  the  union  yields. 
Well,  the  very  counterpart  of 
this  amusing  operation  is  repeated 
by  the  clever  "  Urchin"  whose 
performances  we  are  considering. 


SUCKER-PLATE  OF  URCHIN.  The  tube  is  his  string  \  the  dilated 
end  with  the  plate  in  it  his  leather ;  his  muscular  power  acts 
like  the  other  urchin's  tread,  to  press  the  bottom  of  the 
sucker  against  the  surface  of  the  rock.  Then  he  pulls  the 
string ;  in  other  words,  he  drags  inwards  the  centre  of  the 
muscular  bottom  of  the  sucker,  which  is,  as  it  were,  sucked 
up  into  the  central  orifice  of  the  plate.  Thus  a  vacuum  is 
formed  beneath  the  middle  of  the  sucker,  on  which  the 
weight  of  the  incumbent  water  and  atmosphere  united 
presses  with  a  force  far  more  than  sufficient  to  resist  the 
weight  of  his  body,  when  he  drags  upon  it,  and,  as  it  were, 
warps  himself  up  to  the  adhering  point. 

Here  is  in  my  cabinet  a  specimen  of  a  Sea-Urchin  of  a 
less  regular  form  :  it  is  the  Heart-Urchin  (Amphidotus 
cordatus).  Essentially,  its  structure  agrees  with  that  of 
the  more  globular  forms,  but  it  is  heart-shaped,  and  the 
two  orifices,  instead  Qf  being  at  opposite  poles,  are  sepa- 
rated only  by  about  one-third  of  the  circumference.  It 
shows  also  singular  impressed  marks  on  its  shell,  as  if 
made  by  a  seal  on  a  plastic  substance. 

But  what  I  chiefly  wish  to  direct  your  attention  to  are 
the  spines.  These  differ  much  from  the  kindred  organs 
in  Ecldnus,  being  far  more  numerous,  very  slender,  curved, 
thickening  towards  the  tip,  and  lying  down  upon  the  shell 
in  the  manner  of  hair,  whence  the  species  is  sometimes 


SEA-UECHINS   AND    SEA- CUCUMBERS.  293 

called  the  Hairy  Sea-egg.  The  array  of  spines  has  a 
glittering  silky  appearance  in  this  dried  state. 

We  will  now  put  a  few  of  them  under  a  low  power  of 
the  microscope,  using  reflected  light  and  a  dark  back- 
ground. They  thus  present  a  very  beautiful  appearance  ; 
elegantly-formed  curved  clubs,  made  of  a  substance  which 
seems  to  be  between  glass  and  ivory,  having  the  whiteness 
of  the  latter  and  the  glittering  brilliance  of  the  former. 
The  entire  surface  appears  to  be  exquisitely  carved,  with 
very  minute  oval  pits,  arranged  in  close-set  lines,  with  the 
most  charming  regularity.  It  is  the  light  reflected  from 
the  polished  bottoms  of  these  pits  that  imparts  to  the  sur- 
face its  sparkling  brilliancy.  At  the  bottom  of  the  spine 
there  is  a  little  depression,  which  fits  a  tiny  nipple  on  a 
wart-like  prominence  of  the  shell,  as  we  saw  in  Echinus ; 
but  a  little  way  above  this  point  there  is  a  singular  pro- 
jection or  shoulder  of  the  calcareous  substance,  which  is 
set  on  at  a  very  oblique  angle  with  the  axis  of  the  spine, 
reminding  one,  as  we  look  at  the  spine  laterally,  of  the 
budding  tines  on  the  horn  of  a  young  deer. 

At  first,  perhaps,  you  are  at  a  loss  to  know  what  pur- 
pose this  shoulder  can  serve  ;  but  by  turning  to  the  shell, 
and  carefully  observing  the  spines  in  their  natural  con- 
nexion with  it,  you  will  observe  that  the  obliquity  of  its 
position  accurately  corresponds  with  the  angle  which  the 
individual  spines  form  with  the  surface  of  the  shell  from 
which  they  spring ;  and  that  the  shoulder  has  its  plane 
exactly  parallel  with  the  latter,  but  raised  a  little  way 
above  it.  Now  the  entire  shell,  during  life,  was  clothed 
with  a  living  flesh,  having  a  thickness  exactly  correspond- 
ing to  the  distance  of  the  shoulder  from  the  shell.  This 
shoulder,  then,  was  an  attachment  for  the  muscular  bands, 
whose  office  it  was  to  move  the  spine  to  and  fro  ;  the  pro- 
jection affording  the  muscles  a  much  better  purchase,  or 
power,  than  they  could  have  had  if  they  had  been  inserted 
into  the  slender  stem  itself. 


294  EVENINGS   AT    THE    MICROSCOPE. 

The  tubercles  on  the  shell  show  a  structure  which  cor- 
responds with  this.  They  are  very  minute ;  but  each  of 
them  is  regularly  formed,  and  is  crowned  with  its  little 
polished  nipple,  on  which,  as  I  have  said,  the  spine  works, 
as  by  a  ball-and-socket  joint.  These  are  arranged  with 
perfect  regularity  in  what  is  called  quincunx  *  fashion ;  and 
by  close  examination  you  will  see  that  each  is  inclosed  in  a 
little  area  formed  by  a  very  low  and  narrow  ridge  of  the 
shell,  which  makes  a  network.  On  the  lateral  portions  of 
the  under  surface  the  meshes  of  this  net  are  particularly 
conspicuous,  and  we  see  that  they  constitute  shallow  hexa- 
gonal cells,  in  the  midst  of  which  is  seated  the  tubercle ; 
yet  not  in  the  exact  centre  either,  but  nearer  the  front 
than  the  back  of  the  area  inclosed. 

Now  this  elevated  ridge  affords,  doubtless,  the  insertion 
of  the  other  end  of  the  muscles  that  move  the  spine  ;  the 
ridge  giving  a  better  purchase  than  a  flat  surface,  as  the 
keel  on  the  breastbone  of  birds  is  deep  in  proportion  to 
the  vigour  of  the  muscles  used  for  flight.  And,  surely, 
the  apparently  trivial  fact  that  the  space  behind  the 
tubercle  is  greater  than  that  in  front,  is  not  without  signi- 
ficance, since  it  implies  a  thicker  muscle  at  that  part, 
which  accords  with  the  circumstance  that  such  would  be 
the  insertion  of  the  muscle-band  whose  contraction  pro- 
duces the  outward  stroke  by  which  the  sand  is  forced  away 
from  the  bed. 

But  what  is  the  need  of  so  much  care  being  bestowed 
upon  the  separate  motion  of  these  thousands  of  hair-like 
spines,  that  each  individual  one  should  have  a  special 
structure  with  special  muscles,  for  its  individual  move- 
ment ?  The  hairs  of  our  head  we  cannot  move  individu- 
ally :  why  should  the  Heart-Urchin  move  his  ?  Truly, 
these  hairs  are  the  feet  with  which  he  moves.  The  animal 
inhabits  the  sand  at  the  bottom  of  the  sea  in  our  shallow 
bays,  and  burrows  in  it.  By  going  carefully,  with  the  lens 
*  See  page  60  for  an  explanation  of  this  term. 


SEA-URCHINS   AND    SEA- CUCUMBERS.  295 

at  your  eye,  over  the  shell,  you  perceive  that  the  spines, 
though  all  formed  on  a  common  model,  differ  considerably 
in  the  detail  of  their  form.  I  have  shown  you  what  may 
be  considered  the  average  shape ;  but  in  some,  especially 
the  finer  ones  that  clothe  the  sides,  the  club  is  slender  and 
pointed  ;  in  others,  as  in  those  behind  the  mouth,  which 
are  the  largest  and  coarsest  of  all,  the  club  is  dilated  into 
a  long  flat  spoon ;  while  in  the  long,  much-bowed  spines 
which  densely  crowd  upon  the  back,  the  form  is  almost 
uniformly  taper  throughout  and  pointed. 

The  animal  sinks  into  the  sand  mouth  downwards.  The 
broad  spoons  behind  the  mouth  come  first  into  requisition, 
and  scoop  away  the  sand,  each  acting  individually,  and 
throwing  it  outwards.  Observe  how  beautifully  they  are 
arranged  for  this  purpose  ;  diverging  from  the  central  line, 
with  the  curve  backwards  and  outwards.  Similar  is  the 
arrangement  of  the  slender  side-spines  ;  their  curve  is  still 
more  backwards,  the  tips  arching  uniformly  outwards. 
They  take,  indeed,  exactly  the  curve  which  the  fore-paws 
of  a  mole  possess  (only  in  a  retrograde  direction,  since 
the  Urchin  sinks  backwards),  which  has  been  shown  to  be 
so  effective  for  the  excavating  of  the  soil,  and  the  throwing 
of  it  outwards.  Finally,  the  long  spines  on  the  back  are 
suited  to  reach  the  sand  on  each  side,  when  the  creature 
has  descended  to  its  depth,  and  by  their  motions  work  it 
inward  again,  covering  and  concealing  the  industrious  and 
effective  miner. 

Thus  we  have  another  instance  added  to  the  ten  thousand 
times  ten  thousand,  of  the  wondrous  wisdom  of  God  dis- 
played in  the  least  and  most  obscure  things.  "  All  Thy 
works  shall  praise  Thee,  0  Lord  !  "  (Ps.  cxlv.  10.) 

There  is  an  order  of  animals  which  naturalists  put  in 
the  same  category  as  the  Sea- Urchins,  but  which  an  un- 
scientific observer  would  regard  as  possessing  little  or  no 
affinity  with  them.  Some  are  like  long,  soft,  and  fleshy 
worms,  and  others,  which  come  the  nearest  to  the  crea- 


296  EVENINGS   AT    THE    MICROSCOPE. 

tares  we  have  been  looking  at,  have  still  the  lengthened 
form,  which,  however,  so  closely  resembles  that  of  a  warty 
angled  cucumber  that  the  animals  I  allude  to  are  familiarly 
called  Sea-cucumbers  (Holothuriada).  The  marine  zoo- 
logist frequently  finds  them  beneath  stones  at  extreme  low 
water,  and  larger  forms — as  big  in  every  direction  as  a 
marketable  cucumber — are  occasionally  scraped  from  the 
bottom  of  the  deep  sea  by  means  of  that  useful  instrument, 
the  dredge.  If  you  drop  one  of  them  into  sea-water,  you 
will  presently  see  from  one  extremity  an  exquisite  array 
unfold,  like  a  beautifully  cut  flower  of  many  petals,  or, 
rather,  a  star  of  ramifying  plumes.  Soon  it  begins  to 
climb  the  walls  of  your  aquarium,  and  then  you  catch  the 
first  glimpse  of  its  affinity  to  the  Urchins  ;  for  the  short 
warts  which  run  in  longitudinal  lines  down  the  body  cor- 
responding to  the  angles,  gradually  lengthen  themselves, 
and  are  soon  perceived  to  be  sucking-feet,  analogous  in 
structure  and  in  function  to  those  with  which  the  Star-fish 
and  the  Sea-Urchin  creep  along. 

But  the  relationship  becomes  more  apparent  still  when 
we  find  that  the  Cucumber  has  a  skeleton  of  calcareous 
substance  deposited  on  exactly  the  same  plan  as  in  the 
Urchin,  viz.,  around  insulated  rounded  cavities.  It  is  true 
you  may  cut  open  the  animal  and  find  nothing  at  all  more 
solid  than  the  somewhat  tough  and  leathery  skin ;  but  a 
calcareous  skeleton  is  there  notwithstanding,  though  in 
truth  only  a  rudimentary  one.  If  we  were  to  cut  off  a 
considerable  fragment  of  the  skin,  and  spread  it  out  to  dry 
upon  a  plate  of  glass,  and  then  cover  it  with  Canada 
balsam,  we  should  find — assisted  by  the  translucency  which 
is  communicated  to  the  tissues  by  the  balsam — that  the 
skin  is  filled  with  scattered  atoms  of  the  calcareous  struc- 
ture, perfectly  agreeing  with  that  with  which  the  solid 
framework  of  the  Urchin  is  built  up,  but  minute  and  iso- 
lated in  the  flesh,  instead  of  being  united  into  one  or  more 
masses  of  definite  organic  form. 


SEA-UBCHINS   AND    SEA- CUCUMBERS.  297 

But  the  atoms  I  speak  of  are  still  more  perfectly  seen 
by  dissolving  the  piece  of  skin  in  boiling  potash,  and 
washing  the  sediment  twice  or  thrice  in  pure  water  ;  this 
may  then  be  spread  upon  a  glass  slide,  and  covered  with  a 
plate  of  thin  glass,  when  it  forms  an  interesting  and  per- 
manent object  for  study.  I  have  here  a  slide  which  is 
the  result  of  such  treatment ;  to  the  naked  eye  it  ap- 
pears sprinkled  with  the  finest  dust,  but  under  magnifying 
power  it  is  seen  to  consist  of  numberless  calcareous 
bodies,  of  great  beauty,  and  very  free  from  extraneous 
matter. 

The  elegance  of  the  forms  is  remarkable,  and  also  their 
uniformity ;  for  though  there  do  occur  here  and  there 
among  them  plates  of  no  regular  shape,  perforated  with 
large  or  small  roundish  orifices,  yet  the  overwhelming 
majority  are  of  one  form,  subject  to  slight  modifications 
in  shape  and  size. 

Neglecting,  then,  the  irregular  pieces,  we  perceive  that 
the  normal  form  is  an  oval  of  open  work,  built  up  by  the 
repetition  of  a  single  element.  That  element  is  a  piece  of 
clear  glassy  material,  highly  refractive,  of  the  shape  of  a 
dumb-bell — two  globes  united  by  a  thick,  short  column. 
The  oval  is  constructed  thus  : — suppose  two  dumb-bells  to 
be  placed  in  contact,  side  by  side,  and  soldered  together, 
there  would  be  of  course  an  oval  aperture  between  their 
columns.  Then  two  other  dumb-bells  are  united  to  these 
in  a  similar  manner,  but  one  on  each  side,  so  that  the 
globes  of  each  shall  rest  in  the  valley  between  the  former 
globes  now  united.  These  then  are  soldered  fast  in  like 
manner ;  and  the  result  is  that  there  are  three  oval  aper- 
tures. The  next  step  is  that  on  the  top  of  the  four  united 
globes  two  other  dumb-bells  stand  erect,  and  lean  over 
towards  each  other  till  their  upper  globes  come  into  con- 
tact, their  lower  ones  remaining  remote  ;  these  are  soldered 
to  the  mass  and  to  each  other,  at  the  points  of  contact, 
leaving  a  fourth  aperture.  The  same  is  repeated  at  the 


298 


EVENINGS    AT    THE    MICROSCOPE. 


opposite  end  by  two  other  dumb-bells  ;  and  the  structure 
is  complete  as  you  see  it.  In  almost  all  cases  the  two 

united  globes  of  these  ter- 
minal elements  are  fused 
into  one  globe,  and  in  not 
a  few  instances  the  ap- 
pearance is  as  if  these 
two  dumb-bells  were  but 
one,  bent  over  in  a  semi- 
circular form ;  but  still  a 
DUMB-BELLS  IN  HOLOTHURiA.  good  many  specimens  oc- 

cur in  which  the  two  dumb-bells  can  be  quite  distinguished 
from  each  other.  The  calcareous  matter  that  solders  the 
elements  together  seems  abundant,  and  has  the  appear- 
ance that  would  be  presented  if  they  had  been  made  of 
solid  glass,  and  united  by  glass  in  a  state  of  fusion ;  the 
latter  having  apparently  run  together,  so  as  to  smooth  and 
round  angles  and  fill  up  chinks,  even  where,  as  is  often 
the  case,  the  globes  themselves  have  only  mutually  ap- 
proximated, and  not  come  into  actual  contact. 

The  average  dimensions  of  these  oval  aggregations  may 
be  .004  inch  in  length,  and  a  little  more  than  .002  in  width ; 
but  some  specimens  occur  which  are  a  little  larger,  and 
others  a  little  smaller  than  this ;  while  the  irregular  plates 
are  sometimes  three  times  the  length. 

Some  of  the  more  worm-like 
members  of  this  class  have, 
however,  a  skeleton  composed 
of  pieces  imbedded  in  their 
skin,  of  even  more  remark- 
able shapes  than  these.  One 
of  these  is  the  Chirodota 
violacea  —  a  native  of  the 
southern  coasts  of  Europe. 
We  have  indeed  a  British 
IN  CHIEODOTA.  SpociQS  of  the  same  genus,  a 


SEA-UBCHINS   AND    SEA-CUCUMBERS.  299 

specimen  of  "which  is  in  my  possession,  but  I  have  vainly 
examined  the  skin  for  any  structure  analogous  to  this.* 
In  the  Mediterranean  species  the  skin,  especially  of  the 
belly-side,  is  described  as  filled  with  plates  exactly  re- 
sembling broad  and  thin  wheels  of  glass,  supported  by 
four,  five,  or  six  radiating  spokes,  and  having  the  inner 
edge  of  the  hoop  cut  into  teeth  of  exceeding  delicacy. 

Another  animal  remarkable  for  the  furniture  of  its  skin 
is  the  genus  Synapta,  which  is  very  similar  in  form,  and 
closely  allied  to  the  Chirodota.  It  is  very  common  in  the 
Adriatic  and  Mediterranean  seas,  but  has  not  yet  been 
taken  on  the  British  coasts.  I  would  counsel  you,  how- 
ever, to  have  your  eyes  open  if  you  have  the  opportunity 
of  searching  our  coasts ;  for,  as  Miiller  found  one  species, 
the  Synapia  inharens,  on  the  shores  of  Denmark,  it  is  not 
at  all  unlikely  that  we  may  possess  either  it  or  some  other. 
Should  it  ever  come  into  your  hands,  slit  open  the  skin  of 
the  belly,  where  you  will  find,  imbedded  in  little  papillae 
or  warts,  some  highly  curious  spicula 
or  calcareous  forms.  Each  consists 
of  an  oblong  plate,  perforated  with 
large  holes  in  a  regular  manner,  and 
having  a  projection  on  its  surface  near 
one  extremity,  to  which  is  jointed  a 

second  piece,  having  the  most  singU-    AXCHOR-PLATE  IN  SYNAPTA. 

larly  true  resemblance  to  an  anchor.  The  flukes  of  this 
anchor  project  from  the  skin,  the  shank  standing  obliquely 
upward  from  the  plate,  to  which  it  is  articulated  by  a 
dilatation,  where  the  ring  would  be,  which  is  cut  into 
teeth,  t 

*  The  most  careful  and  repeated  search  has  not  availed  me  to 
find  in  the  skin  the  least  trace  of  calcareous  atoms ;  but  this  may  pos- 
sibly be  because  I  had  unfortunately  preserved  my  specimen  in  acetate 
of  alumina,  and  the  acetic  acid  has  perhaps  dissolved  the  lime. 

t  Since  the  printing  of  the  above,  an  admirable  paper  has  appeared 
in  the  proceedings  of  the  Zoological  Society  of  London,  by  Messrs. 
Woodward  and  Barrett,  "  On  the  Genus  Synapta."  These  authors  in- 


300  EVENINGS   AT   THE    MICEOSCOPE. 

Among  the  multitude  of  transparent  creatures  that  swim 
in  the  open  sea,  few  are  more  interesting  than  the  infant 
state  of  the  very  animals  that  we  have  lately  been  examin- 
ing ;  the  Sea-Urchins  and  their  allies.  It  is  a  productive 
way  of  obtaining  subjects  for  microscopic  research,  to  go 
out  in  a  boat  on  a  quiet  summer's  day,  especially  in  the 
afternoon,  when  the  sun  has  been  shining,  or  when  even- 
ing is  waning  into  night,  and,  with  a  fine  muslin  net 
stretched  over  a  brass  ring  at  the  end  of  a  pole,  skim  the 
surface  of  the  smooth  sea.  At  intervals  you  take-in  your 
net,  and  having  a  wide-mouthed  glass  jar  ready,  nearly 
filled  with  sea-water,  invert  the  muslin  in  it,  when  your 
captures,  small  and  great,  float  off  in  the  receiver.  After 
a  few  such  essays,  unless  you  have  very  bad  success  in- 
deed, you  will  see  even  with  the  naked  eye,  but  much 
more  with  a  lens,  that  the  water  in  your  jar  is  teeming 


form  us  that  two  species  of  Synapta  are  found  in  the  British  seas,  one 
of  which,  the  Chirodota  digitata  of  E.  Forbes,  is  the  species  referred  to 
in  the  text  as  being  in  my  own  possession.  Its  skin  proves  to  be  studded 
with  anchors,  not  with  wheels,  and  it  is  on  this  ground  referred  to  the 
genus  Synapta. 

Still  later  (See  Qu.  Journ.  Micr.  Sci.  for  1862,  p.  131),  Dr.  Wyville 
Thompson  has  obtained  Synapta  inhcerens  in  the  Irish  Loughs  of  Belfast 
and  Strangford.  In  his  admirable  paper  on  the  infancy  and  develop- 
ment of  this  curious  creature,  elaborately  illustrated,  he  has  traced  the 
gradual  formation  of  the  calcareous  spiculae,  from  their  trst  indication. 
The  anchor  first  appears  as  a  straight  rod  sharp  at  both  ends.  One  end 
gradually  becomes  knobbed ;  the  knob  extends  on  each  side,  giving  the 
rod  a  T  form ;  and  soon  the  arms  curve  backward,  giving  the  anchor- 
form.  Then  the  basal  end  becomes  dilated.  Hitherto  no  trace  of  the 
plate  has  appeared  ;  but  now  a  small  glassy  needle  is  seen  lying  across 
the  shank  near  the  base.  Each  extremity  of  this  now  branches,  and 
these  again  branch,  the  points  meeting  and  uniting  here  and  there, 
until  at  length  the  plate  is  gradually  mapped  out.  As  yet  the  openings 
left  by  the  uniting  network  are  smooth-edged ;  but  the  glassy  network 
gradually  strengthens,  and  the  edges  of  the  holes,  now  no  longer  meshes 
of  a  net,  but  orifices  in  a  plate,  are  studded  with  teeth  all  round.  I 
refer  my  readers,  for  much  information  of  the  deepest  interest,  to  this 
very  valuable  memoir. 


SEA-URCHINS    AND    SEA-CUCUMBERS.  301 

with  microscopic  life  ;  and  though  many  of  your  captives 
will  not  long  survive  the  loss  of  their  freedom,  still  mean- 
while you  may  secure  many  an  interesting  object,  and 
examine  it  while  yet  the  beauty  and  freshness  of  life  re- 
main. And,  moreover,  with  care  and  prudence,  some 
selected  subjects  may  be  maintained  in  vigour,  at  least 
long  enough  to  afford  you  valuable  information  on  the 
habits,  economy,  metamorphosis,  and  development  of  ani- 
mals, of  which  even  the  scientific  world  knows  as  yet  next 
to  nothing. 

I  have  just  been  so  fortunate  as  to  obtain  in  this  way 
one  of  our  Sea-Urchins  in  its  larva  state,  and  have  it  now 
in  the  thin  glass  trough  which  is  on  the  stage  of  the  micro- 
scope. It  is  just  visible  to  the  unassisted  sight  as  a  slowly 
moving  point  in  the  clear  water,  when  the  vessel  is  held  up 
to  the  light ;  but  with  the  low  power  which  I  am  now 
using,  it  is  distinctly  made  out  in  all  its  parts,  and  is  an 
object  of  singular  elegance  and  beauty. 

It  is,  as  you  see,  somewhat  of  the  figure  of  a  helmet, 
the  crest  rising  to  a  perpendicular  point,  which  is  rounded, 
the  vizor  or  mask  descending  far  down,  and  ending  in  two 
points,  and  a  long  ear  hanging  down  on  each  side,  so  as  to 
reach  the  shoulders  of  the  wearer.  Of  course  such  com- 
parisons are  fanciful,  but  they  assist  one  in  intelligible 
description. 

Now,  the  entire  helmet  is  composed  of  a  gelatinous 
flesh  of  the  most  perfect  transparency,  so  that  we  can  see 
with  absolute  clearness  everything  that  is  within  it.  And  the 
first  thing  that  strikes  us  is,  that  a  frame- work  or  skeleton 
of  extreme  delicacy,  composed  of  glassy  rods,  supports  the 
whole  structure.  Look  carefully  at  this,  and  mark  its 
symmetry  and  elegance.  There  is,  then,  first,  a  rod  which 
passes  through  the  crest  perpendicularly,  and  carries  at 
its  lower  extremity  a  horizontal  ring.  To  the  opposite 
sides  of  this  ring  are  soldered  two  other  very  slender  rods, 
passing  down  nearly  in  a  perpendicular  direction,  but  a 


302  EVENINGS    AT    THE    MICROSCOPE. 

little  diverging ;  and  two  other  shorter  rods  pass  down 
from  the  front  of  the  ring,  parallel  to  these.  After  a  while 
each  lateral  pair  of  rods  is  united  by  a  short  cross-piece, 
and  the  result  is  four  lengthened  rods,  two  of  which  go 
down  through  the  vizor  into  the  chin-points,  and  two 
larger  and  stouter  ones  through  the  ears  into  the  shoulder- 
points.  This,  then,  is  the  solid  skeleton,  the  interest  of 
which  is  much  enhanced,  when  we  observe  that  it  is 
formed,  on  the  common  plan,  out  of  perforated  lime-glass, 
the  two  ear-rods  and  the  crest-rod  being  pierced  with  a 
regular  series  of  oval  holes,  and  bearing  on  their  edges 
corresponding  projecting  points. 

Now,  to  turn  again  to  the  gelatinous  flesh.  The  inner 
surface  of  the  vizor,  or  that  which  would  be  in  contact 
with  the  face  of  the  wearer,  supposing  it  to  be  a  real 
helmet,  has  a  great  squarish  orifice  with  a  thickened 
margin,  which  we  see  by  its  movements  to  be  highly  sen- 
sitive and  contractile.  This  square  orifice  is  the  mouth  of 
the  larva,  and  it  leads  into  a  cavity  in  the  upper  part  of 
the  vizor,  which  is  the  gullet ;  and  this  in  its  turn  ter- 
minates in  a  narrowed  extremity,  which  passes  into  the 
orifice  of  a  greater  and  higher  cavity,  the  lip  of  which 
embraces  it  just  as  the  bung-hole  of  a  barrel  receives  and 
embraces  the  tube  of  a  funnel.  The  latter  cavity  occupies 
the  chief  part  of  the  volume  of  the  helmet,  the  four  rods 
diverging  to  inclose  it.  It  is  the  stomach. 

It  adds  to  the  beauty  of  the  little  helmet-shaped  crea- 
ture, that  while  the  greater  portion  of  the  substance  is  of 
the  most  colourless  transparency,  the  summit  of  the  crest 
and  the  tips  of  the  shoulder-points  are  tinged  with  a  lovely 
rose  red.  The  whole  exterior  surface  is,  moreover,  studded 
with  those  minute  and  glandular  specks,  with  which  every 
part  of  the  adult  Urchin  is  covered;  and  the  light  is 
reflected  from  the  various  prominences  with  sparkling 
brilliancy. 

The  little  creature  moves  through  the  water  with  much 


SEA-UBCHINS   AND   SEA-CUCUMBEBS.  303 

grace  and  with  a  dignified  deliberation ;  the  crest  being 
always  uppermost,  and  the  perpendicular  position  invari- 
ably maintained.  It  does  not  appear  capable  of  resting, 
its  movements  depending  on  incessantly  vibrating  cilia. 
These  organs  we  perceive  densely  cloth- 
ing the  long  ear-pieces,  but  more  especi- 
ally accumulated  and  more  vigorous  in  a 
thickened,  fleshy  band,  which  passes 
partly  round  the  whole  helmet,  at  the 
origin  of  these  pieces. 

You  do  not  discern  the  slightest  re- 
semblance of  form  between  this  little 
slowly- swimming  dome  and  the  spined 
and  boxed  Urchin  which  crawls  over 
the  rocks ;  and  you  wonder  by  what 
steps  the  tiny  atom  of  one-fortieth  of  an 
inch  in  length  is  led  to  its  adult  stage. 
Fortunately  I  can  satisfy  your  curiosity 
on  this  point,  not  indeed  from  my  own 
observation,  but  from  those  of  Professor 
Johann  Miiller,  whose  discoveries  of  the 

•j  -I  f  ,-,  J     l_i      J         J  •      LARVA   OP   SEA-URCHIN*. 

developments  ot  these  and  kindred  ani- 
mals are  among  the  most  interesting,  because  the  most 
startling,  of  the  marvels  which  modern  zoology  has  revealed 
to  us.  The  whole  process  is  full  of  surprising  details,  to 
which  the  change  of  the  caterpillar  to  a  chrysalis,  and  the 
chrysalis  to  a  butterfly,  presents  no  parallel,  wonderful  as 
those  changes  of  form  appear  and  are.  There  we  have 
but  modifications  of  outward  form,  produced  by  the  succes- 
sive moults  or  castings  of  the  external  skin,  and  the 
gradual  growth  of  the  animal,  which  has  from  the  first 
been  present,  though  veiled.  But  the  construction  of  the 
Sea-Urchin  is  by  no  means  a  process  of  skin-casting,  nor 
has  it  any  recognised  parallel  in  the  whole  economy  of 
natural  history.  It  is  a  development  perfectly  unique.  I 
will  endeavour  to  make  you  acquainted  with  the  results 


304  EVENINGS    AT    THE    MICE03COPE. 

arrived  at  from  the  researches  of  the  eminent  German 
zoologist,  to  whom  we  are  indebted  for  almost  all  we  know 
on  the  matter. 

Let  me  first  premise  that  this  beautiful  helmet- shaped 
creature  is  not  the  future  Urchin  ;  and,  strange  to  say,  that 
only  a  very  small  portion  of  the  present  structure,  namely, 
the  stomach  and  gullet,  will  enter  into  its  composition. 
The  helmet  is  a  kind  of  temporary  nurse,  within  which  the 
future  Urchin  is  to  be  formed,  and  by  which  it  is  to  be 
carried  from  place  to  place  by  its  ciliary  action,  while  the 
young  animal  is  gradually  acquiring  the  power  of  inde- 
pendent life ;  when  the  whole  constitution  of  the  nurse 
will  waste  away  and  vanish  ! 

The  first  trace  of  the  young  Urchin  is  a  filmy  circular 
plate,  which  is  not  symmetrical  with  the  helmet,  nor 
formed  even  on  the  same  plane,  but  appears  obliquely 
fixed  on  the  interior  of  the  stomach,  on  one  side,  close  to 
the  arch  of  transparent  flesh  which  stretches  from  one  of 
the  points  of  the  vizor  to  one  of  the  ear-points.  Herr 
Miiller  compares  the  larva  (which  is  not  helmet-shaped  in 
every  species)  to  a  clock-case,  of  which  the  vizor,  with  its 
hanging  gullet  and  mouth,  forms  the  pendulum ;  and  then 
the  newly  formed  disk  represents  the  face  of  the  clock, 
only  it  is  put  on  the  side  instead  of  the  front.  Now  this 
tiny  disk  gradually  grows  into  the  form  and  assumes  all 
the  organs  of  the  Urchin,  while  the  enveloping  nurse,  flesh, 
rods,  and  all,  wastes  away  to  nothing. 

The  disk,  soon  after  ite  appearance,  is  seen  to  bear  pro- 
minences on  its  surface,  in  which  is  traced  the  figure  of  a 
cinque-foil,  the  elements  being  five  warts  set  symmetri- 
cally. These  lengthen  and  grow  into  suckers,  essentially 
identical  with  those  of  the  adult,  but  most  dispropor- 
tionately large.  In  the  five  triangular  interspaces  between 
these,  little  points  and  needles  of  solid  calcareous  glass 
begin  to  form,  very  much  like  the  crystals  that  shoot 
across  a  drying  drop  of  a  solution  of  some  salt ;  these  catch 


SEA-URCHINS   AND    SEA-CUCUMBERS. 


805 


and  unite,  first  into  T-,  and  then  into  H  -forms,  and 
then  into  irregular  networks.  Meanwhile,  fleshy  cylindrical 
columns  spring  up  from  the  surface,  one  in  each  of  these 
interspaces,  and  presently  develop  within  their  substance  a 
similar  framework  of  porous  glass  ;  these  soon  manifest  them- 
selves to  be  the  spines,  and  each  is  seated  on  a  little  nucleus 
of  network,  on  which  it  possesses  the  power  of  rotating. 

At  the  same  time  pedicellariae  begin  to  be  formed ;  and, 
what  is  specially  marvellous,  they  are  first  seen,  not  on 
the  disk,  which  alone  is  to  be  the  future  Urchin,  but  on 
the  interior  wall  of  the  helmet,  which  is  even  now  in  pro- 
cess of  being  dissipated,  and  even  on  the  opposite  side  to 
that  which  carries  the  disk.  They  commonly  appear  four 
in  number,  arranged  in  two  pairs ;  and  one  can  see  in  them 
— they  being,  like  the  suckers,  large  out  of  all  proportion 
to  the  disk — the  stem,  and  the  three -leaved  heads,  which 
already  exercise  their  characteristic  snapping  movements. 

The  disk  is  meanwhile  enlarging  its  area;  and  the 
spines  and  suckers,  gradually  lengthening,  at  length  push 
themselves  through  the  walls  of  the  helmet ;  the  hanging 
points  and  crest  of  which  are 
fast  diminishing  by  a  kind  of 
insensible  absorption ;  the  ci- 
liary movements  become  less 
vigorous,  and  the  mouth  closes 
up.  But,  correspondently,  the 
Urchin  is  beginning  to  acquire 
its  own  independent  power  of 
locomotion ;  for  the  suckers, 
now  ever  sprawling  about,  are 
capable  of  adhering  to  any 
foreign  body  with  which  they 
come  into  contact,  and  of  drag- 
ging the  whole  structure  about*  by  their  proper  contractions. 
The  cilia  that  cover  the  thickened  fringing  band  still 
exercise  then:  powers,  and  are  the  last  to  disappear. 


YOUNG  SEA-URCHIN: 
DEVELOPMENT  OF  DISK. 


306  ,    EVENINGS   AT    THE    MICROSCOPE. 

When  the  disk  has  grown  to  such  an  extent  as  to  spread 
over  about  half  of  the  larval  stomach,  very  little  remains 
of  the  helmet,  except  the  middle  portions  of  the  glassy 
rods  and  the  ciliary  bands  ;  all  the  rest  of  this  exquisitely 
modelled  framework  having  vanished  by  insensible  degrees, 
no  one  knows  how  or  where.  The  stomach  and  gullet, 
indeed,  are  gradually  sucked  into  the  ever-growing  disk ! 
but  all  the  rest,  flesh  and  rods,  fringes,  bands,  and  cilia, 
waste  away  to  nothing. 

The  mouth  of  the  larva  has  no  connexion  with  the 
mouth  of  the  Urchin.  The  little  isolated  patches  of  glassy 
network  continue  to  spread  through  the  flesh  of  the  disk, 
until  the  whole  forms  one  uniform  structure,  and  con- 
stitutes a  series  of  plates.  The  mouth  is  that  spot  in  the 
centre,  over  which  the  calcareous  frame  is  last  extended ; 
and  it  is  first  distinguishable  by  the  appearance  of  five 
glassy  points,  which  soon  develop  themselves  into  the  five 
converging  jaws,  which  we  see  forming  such  a  curious 
apparatus  on  the  inferior  side  of  the  Sea-Urchin. 

Actual  observation  has  not  traced  the  infant  animal 
beyond  this  stage  of  the  development ;  but  Professor 
Miiller  has  taken  specimens,  swimming  in  the  sea,  in 
which  scarcely  a  rudiment  of  the  larva  remained.  They 
had  the  form  of  round  flattened  disks,  which  freely  moved 
their  spines,  and  crawled  about  the  sides  of  the  vessel  in 
which  they  were  kept  by  means  of  their  suckers,  exactly  in 
the  manner  of  the  adult  Urchin. 

"Thus  ends  this  strange,  eventful  history;"  and  in 
reviewing  it,  one  can  scarcely  avoid  being  impressed  with 
a  sense  of  the  majesty  of  God  in  these  His  humbler  works. 
By  what  wonderful,  what  unexpected  roads  does  He  arrive 
at  the  completion  of  His  designs !  and  if  such  things  as 
these  are  only  now  bursting  upon  our  'knowledge,  after 
thousands  of  years  of  man's  familiar  contact  with  the 
inferior  creatures,  how  many  more  wonders  may  yet 
remain  to  be  unfolded,  as  science  pursues  her  investiga- 
tions into  the  Divine  handiwork ! 


JELLY-FISHES.  807: 


CHAPTER  XVII. 

JELLY-FISHES. 

As  this  afternoon  was  delightfully  calm  and  warm,  the 
very  model  of  an  autumnal  day,  I  took  my  muslin  ring- 
net  and  walked  down  to  the  rocks  at  the  margin  of  the 
quiet  sea.  Nor  was  I  disappointed;  for  the  still  water, 
scarcely  disturbed  by  an  undulation,  and  clear  as  crystal, 
was  alive  with  those  brilliant  little  globes  of  animated  jelly, 
the  Ciliograde  and  Naked- eyed  Medusae,  apparently  little 
more  substantial  than  the  clear  water  itself.  Multitudes 
of  them  were  floating  on  the  surface,  and  others  were  dis- 
cerned by  the  practised  eye,  at  various  depths,  shooting 
hither  and  thither,  now  ascending,  now  descending,  now 
hanging  lightly  on  their  oars,  and  now,  as  if  to  make  up 
for  sloth,  darting  along  obliquely  with  quickly-repeated 
vigorous  strokes,  or  rolling  and  revolving  along,  in  the 
very  wantonness  of  humble  happiness. 

After  gazing  awhile  with  admiration  at  the  undisturbed 
jollity  of  the  hosts,  I  made  a  dip  with  my  net,  the  interior 
of  which,  on  lifting  it  from  the  water,  was  lined  with 
sparkling  balls  of  translucent  jelly.  They  were  far  too 
numerous  to  allow  me  to  transfer  them  all  to  captivity ; 
they  would  soon  have  choked  up  and  destroyed  one 
another  ;  I  therefore  selected  the  finest  and  most  interest- 
ing, shaking  an  example  or  two  of  each  kind  into  my  glass 
jar  of  sea-water,  where  they  immediately  began  to  frolic 
and  revel  as  if  still  in  the  enjoyment  of  unrestricted  liberty. 
And  here  they  are. 

Among  these  bright  and  agile  beings  which  are  shooting 
x  2 


808  EVENINGS   AT   THE    MICROSCOPE . 

» 

their  wayward  traverses  across  each  other,  and  intertwin- 
ing their  long  thread-like  tentacles,  we  will  select  one  or 
two  for  examination,  as  samples  of  their  kindred.  And 
first  let  me  separate  this  active  little  Beroe  (Cydippe  pomi- 
formis),  which  I  dip  out  with  a  tea-spoon  and  transfer  to 
this  other  glass  jar,  that  we  may  watch  its  form  and 
movements  unaffected  by  the  presence  of  its  companions. 

We  see,  then,  a  little  ball,  almost  perfectly  globular, 
except  that  a  tiny  wart  marks  one  pole,  of  the  size  of  a 
small  marble,  and  apparently  turned  out  of  pure  glass,  or 
ice,  or  jelly — according  to  your  fancy, — perfect  transpa- 
rency and  colourlessness  being  its  characteristics,  so  much 
that  it  is  not  always  easy  to  catch  sight  of  the  little  crea- 
ture, except  when  we  allow  the  light  to  fall  on  the  jar  in  a 
particular  direction.  From  two  opposite  sides  of  the  globe 
proceed  two  threads  of  great  length  and  extreme  tenuity, 
which  display  the  most  lively  and  varied  movements. 

These  filaments  shall  occupy  us  for  a  few  moments.  We 
trace  them  to  their  origin,  and  find  that  they  proceed  each 
from  the  interior  of  a  lengthened  chamber,  on  each  of  two 
opposite  sides  of  the  animal.  Suddenly,  on  the  slightest 
touch  of  some  foreign  object,  one  of  the  threads  is  con- 
tracted to  a  point  and  concealed  within  its  chamber,  but  is 
presently  darted  forth  again.  When  the  lovely  globe 
chooses  to  remain  still,  the  threads  hang  downward,  gra- 
dually lengthening  more  and  more,  till  their  extremities 
lie  along  the  bottom  of  the  jar,  extended  to  a  length  of  six 
inches  from  the  chamber.  Then  we  see  that  this  delicate 
thread  is  not  simple,  but  is  furnished  along  one  side, 
throughout  its  length,  at  regular  distances,  with  a  row  of 
secondary  filaments,  which  project  at  right  angles  from  the 
main  thread. 

These  secondary  filaments  constitute  an  important  ele- 
ment in  the  charm  which  invests  this  brilliant  little  crea- 
ture. They  are  about  fifty  in  number  on  each  thread,  and 
some  of  them  are  half  an  inch  long,  when  fully  extended, 


JELLY-FISHES.  809 

but  it  is  seldom  that  we  see  them  thus  straightened  ;  for 
they  are  ever  assuming  the  most  elegant  spiral  coils,  which 
open  and  close,  extend  and  contract,  with  an  ever  chang- 
ing vivacity.  The  animal  has  a  very  perfect  control  over 
each  thread,  as  well  as  over  each  individual  secondary 
filament.  They  are,  either  together  or  separately,  fre- 
quently projected  from  their  chambers  to  their  full  extent 
by  one  impulse  ;  sometimes  the  extension  is  arrested  at 
any  stage,  and  then  proceeded  with,  or  the  thread  is  par- 
tially or  entirely  retracted.  Sometimes  the  secondary  fila- 
ments are  coiled  up  into  minute  balls,  scarcely  perceptible, 
or  only  so  as  to  give  to  the  main  thread  the  appearance  of 
small  beads  remotely  strung  on  a  fine  hair ;  then  a  few 
uncoil  and  spread  divergently ;  contract  again,  and  again 
unfold;  or  many,  or  all,  interchange  these  actions  toge- 
ther, with  beautiful  regularity  and  uniformity,  repeating 
the  alternation  for  many  times  in  rapid  succession. 

The  beauty  and  diversity  of  the  forms  assumed  by  these 
elegant  organs  beguile  us  to  watch  them  with  unwearied 
interest,  and  we  wonder  what  is  their  function.  For,  with 
all  our  watching,  this  is  by  no  means  clear.  They  are 
certainly  not  organs  of  motion.  At  times  it  seems  as  if 
they  were  cables  intended  to  moor  the  animal,  while  it 
floats  at  a  given  depth ;  for  we  see  them  with  their  ex- 
tremities spread  upon  the  bottom,  to  which  they  appear 
to  have  a  power  of  adhering,  thus  forming  fixed  points, 
from  which  the  little  globe  rises  and  falls  at  pleasure, 
shortening  or  lengthening  its  delicate  and  novel  cables, 
maintaining  all  the  while  its  erect  position. 

When  the  Cydippe  swims,  however,  which  it  does  with 
great  energy,  the  threads  seem  unemployed,  streaming 
loosely  behind,  and  evidently  taking  no  part  in  the  pro- 
gression, though  still  adding  beauty  and  grace  to  the  tout 
ensemble.  The  organs  by  which  the  sprightly  motions  of 
the  whole  animal  are  effected  are  of  quite  another  charac- 
ter, and  shall  now  engage  our  attention. 


310 


EVENINGS   AT   THE   MICROSCOPE. 


You  have  doubtless  observed,  while  gazing  on  the  ani- 
mal, a  peculiar  glittering  appearance  along  its  sides, 
mingled  in  certain  lights  with  brilliant  rainbow-reflections. 
Now  let  us  take  an  opportunity,  when  it  approaches  the 
side  of  the  glass,  to  examine  this  appearance  with  a  lens. 
The  globe,  you  see,  is  marked  by  longitudinal  bands,  eight 
in  number,  set  at  equal  distances,  and  ranging  like  meri- 
dians, except  that  they  do  not  quite  reach  to  either  pole. 
These  bands  are  the  seats  of  the  motile  organs,  which  are 
highly  curious,  and  in  some  sort  peculiar. 

Each^band  is  of  considerable  width  in  the  middle,  but 
becomes  narrower  towards  the  extremities.  It  carries  a 


number— usually  from  twenty  to  thirty — of  flat  thin  mem- 
branous fins,  set  at  regular  distances,  one  above  the  other, 
which  may  be  considered  as  single  horizontal  rows  of  cilia, 
agglutinated  together  into  flat  plates.  Each  plate  has  a 
rapid  movement  up  and  down,  from  the  line  of  its  inser- 
tion into  the  band,  as  from  a  hinge,  and  thus  striking  the 
water  downwards,  like  a  paddle.  The  whole  band  may  be 
likened  to  the  paddle-wheel  of  a  steamer,  except  that  the 


JELLY-FISHES.  311 

paddles  are  set  in  a  fixed  line  of  curvature  instead  of  a 
revolving  circle.  The  effect,  however,  is  exactly  the  same  : 
that  of  paddling  the  beautiful  little  globe  vigorously  through 
the  water.  The  prismatic  colours  are  produced  by  the 
play  of  light  on  their  glittering  surfaces,  which  are  ever 
presented  to  the  eye  of  the  beholder  at  changing  angles. 

We  rarely  see  these  rows  of  paddle-fins  wholly  at  rest, 
but  occasionally  one  or  two  bands  will  be  alone  in  a  state 
of  vibration ;  or  one  or  more  will  suspend  their  action 
while  the  rest  are  paddling.  Sometimes  in  a  band  that  is 
at  rest,  a  minute  and  momentary  wave  will  be  seen  to  run 
rapidly  along  its  length.  All  these  circumstances  show 
that  the  ciliary  motion  is  perfectly  under  the  control  of 
the  animal's  will,  not  only  in  the  aggregate,  but  in  every 
part. 

In  an  excellent  memoir  on  this  animal  by  Mr.  R.  Patter- 
son, of  Belfast,*  there  are  some  interesting  observations 
on  the  power  of  its  tissues  to  become  tinged  with  extra- 
neous colours,  a  fact  which  may  be  useful  to  you  in  your 
researches,  as  enabling  you  with  more  ease  and  precision 
to  demonstrate  the  internal  structure. 

"  From  the  inconsiderable  quantity  of  solid  material " 
(remarks  this  observer)  "which  enters  into  the  body  of 
the  Beroes,  and  the  rapid  circulation  of  water,  which  is 
apparent  throughout  their  frame,  we  would  naturally  sup- 
pose that  any  tinge  which  the  body  might  accidentally 
acquire  would  be  extremely  fugitive.  It  was  found,  how- 
ever, to  be  much  less  so  than  a  priori  would  have  been 
expected.  My  attention  was  drawn  to  this  peculiarity  by 
the  circumstance  of  all  my  glass  vessels  being  one  evening 
occupied  by  Beroes  and  Crustacea,  so  as  to  compel  me  to 
place  a  small  Medusa  in  a  tin  vessel,  which  chanced  to  be 
rusted  at  the  seams.  Next  morning  the  colourless  appear- 
ance of  the  animal  was  changed  into  a  bright  yellow,  which 
appeared  to  pervade  every  part,  and  doubtless  arose  from 
*  "Trans.  Boy.  Irish  Academy,"  vol.  xix.  pt.  1. 


312  EVENINGS   AT   THE   MICROSCOPE. 

the  oxide  of  iron,  diffused  through  the  sea- water.  This 
tint  remained  during  the  entire  day,  although  the  animal 
was  transferred  to  pure  sea- water.  Wishing  to  try  if  the 
vessels  of  the  Beroe  would  become  distinct,  if  filled  with  some 
coloured  fluid  from  which  the  animal  could  suddenly  be  with- 
drawn, and  viewed  through  the  usual  transparent  medium 
of  sea-water,  I  placed  a  Beroe  in  a  weak  infusion  of  saffron. 
At  the  end  of  twenty  minutes  its  colour  had  undergone  a 
perceptible  change.  I  allowed  it,  however,  to  remain  im- 
mersed for  about  six  or  seven  hours,  when  it  had  assumed 
a  bright  yellow  hue.  It  was  then  placed  in  pure  sea- 
water,  but  retained  its  yellow  colour  for  twenty-four  hours 
afterwards ;  and  though  it  gradually  become  fainter,  it 
was  very  perceptible  even  at  the  expiration  of  forty-eight 
hours." 

I  am  sure  you  will  pardon  my  interrupting  your  micro- 
scopic gazings  for  a  moment  by  quoting  the  following 
charming  lines  by  the  Rev.  Dr.  Drummond,  which  were 
elicited  by  his  having  watched  with  pleasure  the  elegant 
form  and  motions  of  this  little  creature  : — 

"  Now  o'er  the  stern  the  fine-meshed  net-bag  fling, 
And  from  the  deep  the  little  Beroe  bring  : 
Beneath  the  sun- lit  wave  she  swims  concealed 
By  her  own  brightness  ;— only  now  revealed 
To  sage's  eye,  that  gazes  with  delight 
On  things  invisible  to  vulgar  sight. 
When  first  extracted  from  her  native  brine, 
Behold  a  small  round  mass  of  gelatine, 
Or  frozen  dew-drop,  void  of  life  or  limb : 
But  round  the  crystal  goblet  let  her  swim 
'Midst  her  own  element — and  lo  !  a  sphere 
Banded  from  pole  to  pole— a  diamond  clear, 
Shaped  as  bard's  fancy  shapes  the  small  balloon 
To  bear  some  sylph  or  fay  beyond  the  moon. 
From  all  her  bands  see  lucid  fringes  play, 
That  glance  and  sparkle  in  the  solar  ray 
With  iridescent  hues.    Now  round  and  round 
She  wheels  and  twirls — now  mounts — then  sinks  profound. 
Now  see  her,  like  the  belted  star  of  Jove, 
Spin  on  her  axis  smooth — as  if  she  strove 


JELLY-FISHES.  818 

To  win  applause— a  thing  of  conscious  sense, 
Quivering  and  thrilling  with  delight  intense. 
Long  silvery  cords  she  treasures  in  her  sides, 
By  which,  uncoiled  at  times,  she  moors  and  rides ; 
From  these,  as  hook-hairs  on  a  fisher's  line, 
See  feathery  fibrils  hang,  in  graceful  twine, 
Graceful  as  tendrils  of  the  mantling  vine ; 
These,  swift  as  angler  by  the  fishy  lake 
Projects  his  fly,  the  keen-eyed  trout  to  take, 
She  shoots  with  rapid  jerk  to  seize  her  food, 
The  small  green  creatures  of  crustaceous  brood : 
Soon  doomed  herself  a  ruthless  foe  to  find, 
When  in  th'  Actinia's  arms  she  lies  entwin'd. 
Here  prison'd  by  the  vase's  crystal  bound, 
Impassable  as  Styx's  nine-fold  round, 
Quick  she  projects,  as  quick  retracts  again, 
Her  flexile  toils,  and  tries  her  arts  in  vain ; 
Till  languid  grown,  her  fine  machinery  worn 
By  rapid  friction,  and  her  fringes  torn, 
Her  full  round  orb  wanes  lank,  and  swift  decay 
Pervades  her  frame  till  all  dissolves  away. 
So  wanes  the  dew,  conglobed  on  rose's  bud  j 
So  melts  the  ice-drop  in  the  tepid  flood : 
Thus,  too,  shall  many  a  shining  orb  on  high 
That  studs  the  broad  pavilion  of  the  sky, 
Suns  and  their  systems,  fade,  dissolve,  and  die." 

While  we  have  been  admiring  our  lovely  little  Cydippe, 
and  comparing  notes  with  other  observers  and  admirers  ; 
other  species  as  small,  as  transparent,  as  sprightly,  and 
scarcely  less  elegant,  have  been  impatiently  waiting  for 
their  share  of  admiration;  shooting  to  and  fro,  tossing 
about  their  little  bells  of  ductile  glass,  and  alternately 
lengthening  and  snatching-in  their  sensitive  tentacles,  in 
astonishment  at  our  stoical  indifference  to  their  charms, 
and  saying,  after  their  manner,  with  the  little  urchin  whose 
feelings  were  hurt  by  the  neglect  of  his  papa's  visitor, — 
"  You  don't  notice  how  beautiful  I  be  !  " 

A  thousand  pardons,  sweet  little  Sarsia  !  We  will  now 
give  you  our  undivided  attention  ;  and  for  this  end  we 
must  take  the  liberty  of  catching  you,  and  of  transferring 
your  translucency  to  solitary  grandeur  in  this  other  glass. 


314  EVENINGS   AT    THE    MICROSCOPE. 

Ha  !  but  you  don't  want  to  be  caught,  eh  ?  And  so  you 
pump  and  shoot  round  and  round  the  jar  as  the  spoon 
approaches  !  Truly  you  are  a  supple  little  subject,  difficult 
to  catch  as  a  flea,  and  difficult  to  hold  (in  a  spoon)  as  an 
eel.  But  here  you  are  at  last,  lying  as  motionless  and  as 
helpless  in  the  silver  as  a  half-melted  atom  of  calf's-foot 
jelly,  to  which,  indeed,  you  possess  no  small  resemblance. 

Look  at  the  pretty  little  Medusa  in  his  new  abode,  at 
once  recovering  all  his  jelly-hood  as  he  feels  the  water 
laving  him,  and  dashing  about  his  new  domain  with  a 
vigour  which  makes  up  for  lost  time. 

It  is  a  tall  bell  of  glass,  a  little  contracted  at  the  mouth 
— its  outline  forming  an  ellipse,  from  which  about  a  third 
has  been  cut  off.  The  margin  of  this  bell  carries  four  tiny 
knobs,  set  at  equal  distances,  and  thus  quartering  the 
periphery ;  and  these  are  the  more  conspicuous  because 
each  one  is  marked  with  a  bright  orange-coloured  speck. 
Physiologists  are  pretty  well  agreed  to  consider  such  specks 
as  these,  on  the  margins  of  the  smaller  Medusa,  as  eyes, — 
rudimentary  organs  of  vision,  capable,  probably,  of  appre- 
ciating the  presence  and  the  stimulus  of  light,  without  the 
power  of  forming  any  visual  image  of  external  objects. 
You  will  not  gain  much  information  about  their  function 
from  microscopic  examination ;  for  all  you  can  discern  is 
an  aggregation  of  coloured  specks  (pigment-granules)  in 
the  midst  of  the  common  jelly. 

The  knobs,  however,  are  connected  with  other  organs ; 
for  from  each  of  them  depends  a  highly  sensitive  and  very 
contractile  tentacle.  Sometimes  one,  or  more,  or  all,  of 
these  organs  hang  down  in  the  water  motionless,  lengthen- 
ing more  and  more,  especially  when  the  bell  is  still,  until 
they  reach  a  length  some  twelve  or  fifteen  times  that  of 
the  bell,  or  umbrella.  Then  suddenly  one  will  be  con- 
tracted, and,  as  it  were,  shrivelled,  to  mere  fragments  a 
quarter  of  an  inch  long ;  then  lengthened  again  to  an 
inch  or  two;  then  shortened  again.  Now  the  little  bell 


JELLY-FISHES.  315 

resumes  its  energetic  pumping,  and  shoots  round  and 
round  in  an  oblique  direction,  the  summit  always  going 
foremost,  and  the  tentacles  streaming  behind  in  long  trail- 
ing lines.  Now  it  is  again  arrested ;  the  bell  turns  over 
on  one  side  and  remains  motionless,  and  the  tentacles, 
"  fine  as  silkworm's  threads,"  float  loosely  in  the  water, 
become  mutually  intertangled,  instantly  free  themselves, 
pucker  and  shrivel  up,  slowly  lengthen,  and  hang  motion- 
less again,  or,  as  the  bell  allows  itself  to  sink  slowly,  are 
thrown  into  the  most  elegant  curves  and  arches. 

Though  these  tentacles  look  at  first  like  simple  threads 
of  extreme  tenuity,  yet  when  viewed  closely  they  are  seen 
to  be  composed  of  a  succession  of  minute  knobs  separated 
by  intervals,  like  white  beads  strung  on  a  thread ;  the 
beads  being  more  remote  from  each  other  in  proportion  as 
the  tentacle  is  lengthened. 

This  structure  is  worthy  of  a  more  minute  investigation. 
We  will  therefore  confine  our  little  Sarsia  in  this  narrow 
glass  trough,  which  is  sufficiently  deep  to  allow  its  whole 
form  to  be  immersed,  though  somewhat  flattened  ;  which 
is  an  advantage,  as  its  movements  are  thereby  impeded. 
Now,  with  a  power  of  300  diameters,  you  see  that  each  of 
the  knobs  of  the  tentacle  is  a  thickening  or  swelling  of  the 
common  gelatinous  flesh,  in  which  are  imbedded  a  score 
or  two  of  tiny  oval  vesicles,  or  bladders,  without  any  very 
obvious  arrangement ;  but  for  the  most  part  so  placed  that 
the  more  pointed  end  of  each  is  directed  towards  the  cir- 
cumference of  the  thickening.  The  intermediate  slender 
portions  of  the  tentacle — the  thread  on  which  the  beads 
are  strung — is  quite  destitute  of  these  vesicles. 

These  little  bodies  are  called  cnida ;  and,  in  the  whole  of 
this  class  of  animals,  and  also  in  that  of  Zoophytes,  they 
play  an  important  part  in  the  economy  of  the  creature.  I 
shall  probably  take  occasion  to  exhibit  them  to  you  under 
conditions  more  favourable  than  are  presented  here,  viz., 
in  the  Sea-Anemones,  where  they  attain  far  greater  dimen- 


316 


EVENINGS   AT   THE   MICROSCOPE. 


sions ;  and  therefore  I  will  merely  say  here  that  each  one 
of  these  tiny  vesicles  carries  a  barbed  and  poisoned  arrow, 
which  can  be  shot  forth  at  the  pleasure  of  the  animal  with 
great  force,  and  to  an  amazing  length  ;  that  hundreds  are 
usually  shot  together  ;  and  that  this  is  the  provision  which 
the  All-wise  God  has  given  to 
these  apparently  helpless  animals 
for  securing  and  subduing  their 
prey. 

There  is,  however,  another 
organ  still  more  conspicuous  in 
our  little  Sarsia,  of  which  I  have 
not  yet  spoken.  As  the  whole 
animal  has  the  most  absolute 
transparency,  we  see  that  the 
roof  of  the  bell  is  much  thicker 
than  the  sides,  and  that  it  gradu- 
ally thins  oflf  to  the  edge.  The 
interior  surface  is  called  the  sub- 
umbrella,  and  it  carries  within 
its  substance  four  slender  tubes, 
which,  radiating  from  the  centre 
of  the  roof,  proceed  to  the  mar- 
gin, where  they  communicate 
with  another  similar  canal  which 
runs  round  the  circumference, 
sending  oflf  branches  into  the 
tentacles.  This  is  the  circulatory 
system;  and  you  may  see,  with 
the  magnifying  power  which  you 

are  at  present  using,  that  a  clear  fluid  is  moving  rapidly 
within  all  these  canals,  carrying  minute  granules ;  not 
with  an  even  forward  current,  but  with  an  irregular  jerk- 
ing movement,  as  if  several  conflicting  eddies  were  in  the 
stream.  Yet  we  discern  that,  on  the  whole,  the  granules 
are  moved  forward  ;  passing  from  the  centre  of  radiation 


/ 


JELLY-FISHES.  317 

towards  the  margin,  when  we  see  them  slip  into  the  mar- 
ginal canal  from  the  several  openings  of  the  radiating 
canals. 

This  is  a  very  simple  and  rudimentary  blood-system. 
There  is  here  no  heart  with  its  pulsations,  no  proper 
arteries  or  veins,  no  lungs  for  oxygenation ;  but  the  pro- 
ducts of  digestion  are  themselves  thus  circulated  through 
the  system.  And  this  brings  me  back  to  the  central  point, 
whence  you  see  depending  the  curious  organ  I  spoke  of. 
A  long  cylinder  of  highly  movable  and  evidently  sensitive 
flesh  hangs  down  from  the  middle  of  the  roof  exactly  like 
the  clapper  of  a  bell ;  and,  as  if  to  add  to  the  resem- 
blance, this  same  clapper  is  suspended  by  a  narrow  cord, 
and  is  terminated  by  a  knob. 

Sometimes  this  whole  organ  is  allowed  to  hang  about  as 
low  as  the  edge  of  the  bell ;  then  it  gradually  lengthens  to 
twice,  thrice,  nay  to  five  times  that  length;  the  tongue 
lolling  out  of  the  mouth  to  a  most  uncouth  distance,  and 
even  the  suspending  cord  (as  I  presume  to  term  the  at- 
tenuated basal  portion)  reaching  far  beyond  the  margin ; 
then,  on  a  sudden,  like  the  tentacles,  the  tongue  is  con- 
tracted, thrown  into  wrinkles,  curled  into  curves,  and  the 
whole  is  sheltered  within  the  concavity;  presently,  how- 
ever, to  loll  out  again. 

This  proboscis-like  organ  is  called  the  peduncle,  and  its 
office  is  that  of  a  stomach,  of  which  the  knob  at  the  end  is 
the  mouth,  having  a  terminal  orifice  with  four  minute  lips. 
The  flexible  substance  and  rapid  motions  of  this  peduncle 
are  suited  to  enable  it  to  seize  small  passing  animals  that 
constitute  its  prey ;  and  I  have  seen  the  Sarsia  in  confine- 
ment seize  with  the  mouth,  and  swallow,  a  newly-hatched 
fish,  notwithstanding  the  activity  of  the  latter.  For  hours 
afterwards,  the  little  green-eyed  fry  was  visible,  the  engulf- 
ment  being  a  very  slow  process ;  but  the  Medusa  never  let 
go  its  hold ;  and  gradually  the  tiny  fish  was  sucked  into 
the  interior,  and  passed  up  the  cavity  of  the  peduncle, 


318  EVENINGS   AT   THE    MICKOSCOPE. 

becoming  more  and  more  cloudy  and  indistinct  as  digestion 
in  the  stomach  dissolved  its  tissues. 

The  greater  portion  of  the  food  is  by  and  by  discharged 
from  the  mouth ;  the  fluids  which  have  been  extracted  from 
it  being  on  the  other  hand  carried  up  through  the  base  of 
the  peduncle,  and  distributed  along  the  four  radiating 
vessels,  conveying  nutrition,  supply  of  wasi^e,  and  growth 
to  all  parts  of  the  system. 

We  may  now  liberate  our  little  Sarsia,  with  thanks  for 
the  gratification  he  has  afforded  us,  to  resume  his  active 
play  among  his  many  companions.  Meanwhile  we  will 
look  for  one  of  another  kind  among  the  group. 

Here  is  a  pretty  and  interesting  species.  Active  it  is, 
but  less  vigorously  rapid  in  its  movements,  than  either  the 
Beroe  or  the  Sarsia.  It  is,  as  you  see,  something  less 
than  a  hemisphere,  or  resembling  a  watch-glass  in  shape, 
about  three-fourths  of  an  inch  in  diameter.  In  general 
character  it  resembles  the  Sarsia,  but  the  peduncle  is 
small,  never  reaching  to  the  level  of  the  margin,  and  its 
mouth  is  terminated  by  four  expanding  fleshy  lips,  which 
are  extremely  flexible  and  versatile. 

The  four  radiating  vessels  here  carry,  just  before  they 
merge  into  the  marginal  canal,  a  dilatation  of  the  common 
flesh,  which,  as  you  see,  bulges  out  the  surface  of  the 
umbrella.  We  will  examine  one  of  these  dilatations  with 
the  microscope. 

It  is,  as  you  perceive,  occupied  by  a  number  of  clear 
globes,  each  of  which  has  another  minute  globose  body  in 
its  interior.  They  are  very  diverse  in  size,  some  being 
very  small,  others  comparatively  large,  and  it  is  to  the 
dimensions  of  these  latter,  that  the  swelling  of  the  surface 
of  the  umbrella  is  due.  These  vesicles  are  the^  eggs  of  the 
animal  considerably  advanced  towards  maturity  ;  and  the 
dilatations  around  the  radiating  vessels  are  the  ovaries. 

The  margin,  however,  presents  us  with  the  most  obvious, 
and  perhaps  the  most  interesting,  points  of  diversity  from 


THAUHANTIAS. 


JELLY-FISHES.  319 

the  Sarsia.    In  the  little  beauty  before  us,  whose  scientific 
name,  by  the  way,  Thaumantias  pilo- 
sella,  I  have  not  yet  told  you, — the  out- 
line is  fringed  with  about  fifty  short  and 
slender  tentacles,  each  of  which  springs 
from  a  fleshy  bulb,  in  which  is  set  a 
speck   of  deep   purple.     These   collec- 
tions of  coloured  granules,  which  I  have 
already   explained   to    be    rudimentary 
eyes,  have  a  very  charming  effect,  and 
give  a  beautiful  appearance  to  the  little  creature,  as  if  its 
translucent  crystalline  head  were  encircled  with  a  coronet 
of  gems. 

You  shall  see  them,  however,  under  circumstances 
which  will  make  them  appear  more  lustrously  gem-like 
still.  Come  with  me,  and  I  will  carry  the  glass  containing 
our  little  Tkaumantias  into  the  next  room.  You  need  not 
bring  the  candle,  or  what  I  am  going  to  show  you  will  be 
quite  invisible. 

Take  hold  of  this  pencil,  and,  having  felt  for  the  glass, 
disturb  the  water  with  it.  Ha  !  what  a  circle  of  tiny 
lamps  flash  out !  You  struck  the  body  of  the  Thaumantias 
with  the  pencil,  and  instantly,  under  the  stimulus  of  alarm, 
every  purple  eye  became  a  phosphoric  flame.  Touch  it 
again ;  again  the  crown  of  light  flashes  out,  but  less  bril- 
liantly; and  each  tiny  lamp,  after  sparkling  tremulously 
for  a  moment,  wanes,  and  the  whole  gradually,  but  quickly, 
go  out,  and  all  is  dark  again. 

But  it  is  tired  of  lighting  up  for  nothing ;  or  its  gas  is 
exhausted ;  or  it  is  become  used  to  the  pencil  and  is  not 
alarmed ;  or, — at  all  events  you  may  knock  it,  and  push 
it,  but  it  refuses  to  shine  any  more.  Back  with  it  then  to 
the  microscope,  and  let  us  see  if  it  possesses  any  other 
points  of  interest  for  us  there. 

Yes  :  we  have  not  exhausted  the  organs  of  the  margin 
yet.  Between  the  tentacles  which  spring  from  bulbs  there 


820  EVENINGS   AT    THE    MICROSCOPE. 

are  a  good  many  more,  far  more  minute,  without  any 
bulbs; — from  four  to  seven  between  every  two  of  the 
primary  ones.  We  won't  mind  these,  but,  bringing  the 
margin  itself  into  focus,  and  moving  it  along  the  stage 
horizontally,  we  presently  see  one  and  another  singular 
organs.  They  are  eight  in  all,  two  being  placed,  but  irre- 
gularly, in  each  of  the  four  quadrants  of  the  circle  formed 
by  the  radiating  canals. 

These  are  organs  of  hearing,  very  closely  similar  to 
those  which  we  see  imbedded  in  the  bosom  of  the  Snail 
and  other  Mollusca.  Here  they  are  comparatively  large, 
and  unusually  well  furnished.  Each  is  a  semi-oval  en- 
largement of  the  flesh  of  the  margin,  in  close  connexion 
with  the  walls  of  the  marginal  canal,  hollowed  so  as  to  in- 
close a  capacious  cavit}7,  in  which  are  placed  a  considerable 
number,— from  thirty  to  fifty  in  this  individual — of  oto- 
lithes,  or  spheres  of  solid,  transparent,  highly  refractive 


OTOLITHES   OF   THAUMANTIAS. 


substance.  They  are  arranged  in  a  double  line,  forming  a 
crescent,  and  those  which  are  nearest  the  centre  are  larger 
than  those  towards  the  extremities  of  the  line.  I  believe 
some  observers  have  seen  oscillatory  and  rotatory  move- 
ments among  these  spherules,  as  in  the  Mollusca ;  but  I 
have  invariably  found  them  motionless  in  all  the  species  of 
Medusa  that  I  have  examined,  as  you  see  them  here. 
One  more  little  beauty  from  our  stock,  and  we  have 


JELLY-FISHES.  321 

done  with  these.  There  is  one  that  moves  among  the 
rest  like  a  bead  of  coral,  the  smallest  of  all,  yet  the  most 
brilliant.  Here  is  another,  and  here  another  of  the  same 
sort ;  which  has  been  named  by  Professor  Edward  Forbes, 
Turris  neglecta,  because  naturalists  before  him  had  ne- 
glected to  notice  it,  just  as  we  have  been  doing,  engrossed 
by  its  larger  brethren. 

Beautiful  as  is  this  little  gem,  it  is  not  so  large  as  a 
dried  pea,  scarcely  larger  than  a  grain  of  hemp-seed.  It 
is  described  as  "  mitre-shaped ;  "  in  other  words  it  is  a  tall 
bell,  with  the  margin  slightly  bent  inwards,  and  the  sides 
a  little  constricted.  The  umbrella  is  thick,  and,  being  very 
muscular,  is  not  so  translucent  as  those  we  have  been  ex- 
amining ;  hence  it  has  a  pellucid  white  appearance.  But 
through  this  shines  its  chief  beauty ;  the  peduncle  is  very 
large,  and  globose  at  the  upper  or  basal  part,  which  is 
usually,  as  here,  of  a  pale  scarlet  or  rich  orange  hue. 

Imbedded  in  this  orange-coloured  flesh  are  seen  many 
points  of  a  lovely  rose-purple,  which  two  colours  blending 
together,  and  softened  by  their  transmission  through  the 
sub-pellucid  umbrella,  have  a  peculiar  brilliancy.  But 
stay !  here  I  have  one  more  advanced  in  age,  which  will 
exhibit  some  peculiarities  of  interest  in  the  economy  of 
these  frail  but  charming  creatures. 

In  this  specimen,  which  is  somewhat  larger  than  the 
former,  the  margin  of  the  umbrella  is  a  little  turned  back, 
displaying  more  clearly  the  peduncle  with  its  brilliant 
ovaries.  These,  too,  are  more  turgid,  and  the  rosy  points 
are  seen  projecting  from  their  interior,  and  some  of  them 
even  ready  to  fall.  And  look  !  here  on  the  bottom  of  the 
glass  are  lying  half-a-dozen  or  more  of  similar  purple 
points,  whose  rich  hue  renders  them  plainly  discernible, 
after  a  slight  searching,  to  the  unassisted  eye.  I  will  col- 
lect one  or  two  with  a  tube  of  glass,  and  submit  them  to 
your  examination  under  the  microscope. 

You  now  discern  that  these  bodies  are  perfectly  oval  in 

Y 


322  EVENINGS   AT    THE    MICROSCOPE. 

form.  One  might,  indeed,  call  them  eggs — for  they  perform 
the  part  of  such  organisms, — but  that  they  have  soft  walls, 
covered  on  their  whole  external  surface  with  fine  vibratile 
cilia,  by  the  action  of  which  they  are  endowed  with  the 
power  of  free  locomotion.  We  see  them,  in  fact,  gliding 
about  the  water  of  the  live-box  under  view,  with  an  even 
and  somewhat  rapid  motion,  which  appears  to  be  guided 
by  a  veritable  will.  Under  this  power  they  are  seen  to  be 
of  a  soft  rich  lake -crimson  hue,  all  over. 

These  little  gemmules  have  a  somewhat  romantic  history 
of  their  own.  I  am  afraid  that  these  we  see  are  too  recent 
to  afford  us  any  help  in  tracing  it,  and  therefore  I  must  be 
satisfied  with  telling  you  what  I  have  observed  of  it  on 
former  occasions. 

After  the  beautiful  little  Coral  Jelly  has  swum  about  a 
few  days,  the  umbrella  begins  to  turn  outward  and  back- 
ward, and  to  contract  more  and  more,  until  at  length  it 
lies  in  shrivelled  folds  around  the  top,  leaving  the  whole 
peduncle  exposed.  Long  before  this,  the  creature  has  lost 
its  power  of  swimming,  and  lies  helpless  on  its  side  upon 
the  bottom.  Meanwhile  the  orange  ovaries  have  swollen ; 
the  purple  gemmules  have  become  developed,  and  have 
gradually  worked  their  way  through  the  ovaries,  and  fallen 
one  by  one  upon  the  bottom.  There  then  they  glide  about 
for  a  little  time,  perhaps  for  a  day  or  so,  by  means  of 
their  vibrating  cilia. 

At  length  each  little  gemmule  loses  its  power  of  wander- 
ing, its  motion  becomes  feebler  and  more  intermitted, 
and  finally  ceases  altogether.  The  little  being  now  rests 
on  some  solid  body, — a  stone  or  a  shell, — to  which  it 
firmly  adheres.  Its  two  extremities  grow  out,  adhering  as 
they  extend,  and  sometimes  branching,  but  still  in  close 
and  entire  contact  with  the  support.  At  length,  after  a 
day  or  two,  from  some  point  of  the  upper  surface  of  this 
creeping  root,  a  kind  of  wart  buds  forth,  and  soon  grows 
into  an  erect  slender  stem,  which  presently  divides  into 


JELLY-FISHES.  823 

four  straight,  slender,  slightly  divergent  tentacles,  which 
grow  straight  upward  to  a  considerable  length.  The  whole 
structure  retains  the  rich  purple  hue  of  the  original 
gemmule. 

Beyond  this  point  I  have  not  pursued  the  history  of  the 
little  Turris  from  personal  observation;  nor  am  I  aware 
that  any  naturalist  besides  has  studied  the  development 
of  this  particular  genus.  But  the  history  of  other  genera 
is  known  ;  and  as  the  phenomena  they  exhibit  are  quite 
parallel  to  those  which  I  have  been  describing,  so  far  as 
these  have  been  traced,  we  may  fairly  conclude  that  there 
is  the  same  parallelism  in  the  subsequent  stages. 

Assuming  this,  then,  the  little  crimson  stem  with  four 
rays, — a  veritable  polype, — buds  four  more  tentacles  in  the 
interspaces,  making  the  total  number  eight ;  these  in  like 
manner  increase  progressively  to  sixteen,  thirty-two,  and 
sixty-four.  It  now  possesses  a  close  resemblance  to  the 
Hydra  of  our  ditches,  only  having  more  tentacles ;  and, 
like  it,  the  Medusa-larva  buds  forth  from  its  sides  young 
Hydra-like  polypes,  which  take  the  form  of  their  imme- 
diate parent,  fall  off,  attach  themselves,  bud  forth  more,  and 
so  on.  All  these  catch  living  prey  with  their  tentacles, 
swallow  them  with  their  mouths,  and  digest  them  with 
their  stomachs,  exactly  like  real  polypes,  and  thus  produce 
generation  after  generation  of  similar  beings. 

Years  may  pass  in  this  stage,  during  which  numberless 
polypes  are  formed.  At  length  the  original  stock,  or  any 
one  of  its  descendants,  takes  on  an  important  change.  Its 
body  lengthens,  and  becomes  cut  as  it  were  into  a  number 
of  rings,  as  if  tied  tightly  round  with  thread,  or  like  the 
body  of  an  Annelid.  These  segments  become  increasingly 
distinct,  until  at  length  each  is  seen  to  be  a  shallow  cup, 
notched  at  its  margin,  and  sitting  in  the  concavity  of  the 

I  one  next  below  it.  This  structure  is  developed  first  in 
those  at  the  free  extremity  of  the  polype,  and  progressively 
downward  ;  and  the  terminal  cups  are  nearly  free,  rocking 

Y2 


324 


EVENINGS   AT   THE   MICROSCOPE. 


in  their  successors  with  every  wave,  while  the  lowest  seg 
ments  are  scarcely  visible  as  such. 

At  length  the  extreme  cup  rocks  and  oscillates  until  the 
slender  thread  of  connexion  is  snapped,  and  it  is  free.  It 
at  once  turns  itself  over,  so  as  to  present  its  concavity 
downwards,  and,  contracting  its  margin  with  the  well- 


TUERI8  AND   ITS  YOUNG. 


known  pulmonic  spasm,  shoots  away  with  the  movement  as 
well  as  the  form  of  a  veritable  Medusa.  The  little  progeny 
has  at  length,  after  passing  through  so  many  changes, 
returned  to  the  image  of  its  parent. 

Such  are,  in  brief,  the  phenomena  of  one  of  the  most 
remarkable  series  of  facts  that  modern  zoology  has  dis- 
covered, and  which  have  been  propounded  under  the  title 
of  the  Law  of  Alternation  of  Generations.* 

*  See  pages  883,  834,  infra. 


ZOOPHYTES.  325 


CHAPTER  XVni. 

ZOOPHYTES. 

IT  is  pleasant  to  go  down  to  the  shore  on  a  bright  autumnal 
morning  at  low  water,  when  the  tide  has  receded  far,  ex- 
posing great  areas  of  wet  sand  and  wildernesses  of  rugged 
rocks  draped  with  black  and  red  weed.  It  is  pleasant  to 
make  our  way  on  cautious  foot  round  some  frowning  point 
whose  base  is  usually  beaten  by  the  billows  ;  to  travel 
among  the  slippery  boulders,  now  leaping  from  one  to 
another,  now  winding  between  them,  now  creeping  under 
their  beetling  roofs ;  to  penetrate  where  we  have  never 
ventured  before,  and  to  explore  with  a  feeling  of  undefined 
awe  the  wild  solitudes  where  the  hollow  sea  growls,  and  the 
grey  gull  wails.  It  is  pleasant  to  get  under  the  shadow  of 
the  tall  elifis  of  limestone,  to  creep  into  low,  arching  caves, 
and  there  to  stoop  and  peer  into  the  dark  pools,  which  lie 
filled  to  the  brim  with  water  as  clear  as  crystal,  and  as  un- 
ruffled as  a  well.  What  little  worlds  are  these  rugged 
basins  I  How  full  of  life  all  unsuspected  by  the  rude 
stone-cutter  that  daily  trudges  by  them  to  and  from  his 
work  in  the  marble  quarry  of  the  cliff  above  !  What  arts, 
and  wiles,  and  stratagems  are  being  practised  there  !  what 
struggles  for  mastery,  for  food,  for  life !  what  pursuits  and 
flights !  what  pleasant  gambols !  what  conjugal  and  pa- 
rental affections  !  what  varied  enjoyments !  what  births ! 
what  deaths !  are  every  hour  going  on  in  these  unruffled 
wells,  beneath  the  brown  shadow  of  the  umbrageous  oar- 
weed,  or  over  the  waving  slopes  of  the  bright  green  Ulva, 
or  among  the  feathery  branches  of  the  crimson  Ceramium ! 


826  EVENINGS    AT    THE    MICROSCOPE. 

I  have  just  been  exploring  some  of  these  rock-wells, 
and  have  rifled  them  of  not  a  few  of  their  living  treasures, 
bringing  home  the  spoils,  that  you  may  share  with  me  in 
the  enjoyment  of  examining  them. 

The  Zoophytes*  are  here  in  their  glory.  Such  places 
as  those  I  speak  of  are  the  very  capitals  of  the  zoophytic 
nation.  Look  at  this  great  leaf  of  the  fingered  Tangle  : 
see  how  its  broad  olive-brown  expanse  is  covered  with  tiny 
forests  of  white  branching  threads,  which  spread  and 
spread  till  they  run  off  into  the  fingers  of  the  much  split 
leaf ;  and  not  only  on  one  side,  for  the  under  surface  is  as 
densely  clad  with  the  shaggy  burden  as  the  upper;  the 
smooth  leathery  tissue  being  covered  with  a  network  of 
creeping  roots,  branching  and  radiating  everywhere,  like 
the  railways  on  BradshaVs  map. 

This  double  forest  is  wholly  composed  of  a  single  species, 
called  Laomedea  geniculata;  nay,  I  believe  it  is  but  one 
single  individual.  That  is  to  say,  the  whole  of  these  mul- 
titudinous ramified  threads  and  stems,  with  their  innu- 
merable polypes,!  have  all  extended  by  gradual  though 
rapid  growth  from  a  single  germ,  and  all  are  connected 
even  now,  so  that  a  common  life  pervades  the  whole. 
But  we  will  look  awhile  at  it  in  detail  till  we  have  mastered 
its  external  features,  and  then  I  will  tell  you  something  of 
its  history  and  economy. 

With  the  unassisted  eye  we* can  discern  plainly  enough 
the  outline  and  plan  of  this  compound  organism.  Along 
the  smooth  and  slippery  surface  of  the  olive  weed  runs  a 

*  From  the  Greek  f«ov  (zoon),  an  animal,  and  $VTOV  (phuton),  a  plant. 
A  term  applied  to  a  large  class  of  animals  bearing  polypes,  and  whose 
entire  skeleton,  called  apolypary  or  polypidom,  more  or  less  resembles  a 
plant  or  tree  in  its  appearance  and  growth. 

The  term  Ccelenterata  is  now  substituted  for  this  in  systematic  natural 
history.  See  Prof.  Greene's  excellent  "  Manual  of  the  Anim.  Kingd." 
ii.  Lond.  1861. 

t  From  the  Greek  n-oXv?  (polus),  many,  and  rovs  (pous),  foot.  A  low 
order  of  animals  with  numerous  tentacles  or  feelers  round  the  aperture 
serving  for  a  mouth,  and  often  bearing  a  strong  resemblance  to  flowers. 


ZOOPHYTES.  327 

fine  thread  of  a  pellucid  white  appearance,  so  firmly  ad- 
herent that  if  you  attempt  to  remove  it  with  a  needle's 
point,  you  find  that  you  only  tear  either  the  leaf  or  the 
thread.  The  course  is  generally  in  a  straight  line,  but 
does  not  ordinarily  pursue  the  same  direction  far,  com- 
monly turning  off  with  an  abrupt  angle  at  intervals  of 
about  an  inch ;  and  thus  meandering  in  a  zig-zag  fashion, 
very  irregularly,  branching  frequently,  and  uniting  with  a 
thread  already  formed,  when  the  creeping  one  has  to 
cross  it. 

Thus  the  basal  network  is  formed;  but  meanwhile, 
from  every  angle,  and  often  from  intermediate  points,  a 
free  erect  thread  has  shot  up — like  the  stem  of  a  tiny 
plant — to  the  height  of  an  inch,  rarely  more ;  not,  however, 
straight,  but  with  frequent  zig-zag  angles,  whence  the 
name  geniculata,  or  "kneed."  At  every  angle  a  slender 
branch  is  sent  forth,  pursuing  the  same  direction  as  that 
of  the  joint  from  the  summit  of  which  it  issued,  and  termi- 
nating in  a  tiny  knob.  In  the  angles  of  some  of  these 
branchlets  are  seated  oblong  vesicles,  twice  or  thrice  as 
large  as  the  terminal  knobs.  And  this  is  pretty  well  all 
that  we  can  make  out  with  the  naked  eye. 

Cutting  carefully  off  with  scissors  a  narrow  strip  of  the 
leaf,  I  drop  it  into  the  parallel-sided  cell  of  glass  half-filled 
with  sea- water,  and  examine  it  first  with  a  low  power  and 
afterwards  with  a  higher.  We  now  see  that  the  creeping 
thread  is  a  tube  of  horny  substance,  flattened  on  its  under 
side,  and  that  the  erect  stems  and  their  branches  are  similar 
tubes,  whose  cavities  are  in  free  communication  with  that 
of  the  creeping  root.  The  wall  is  thin,  and  perfectly 
transparent  and  colourless  ;  the  whiteness  of  the  whole 
being  dependent  on  a  soft  medullary  core  of  living  jelly, 
which  permeates  the  whole  structure,  on  which  the  horny 
sheath  is  as  it  were  moulded. 

This  medulla  is  pierced  with  a  canal,  through  which  a 
fluid  circulates,  carrying  along  numerous  minute  granules 


328 


EVENINGS    AT    THE    MICROSCOPE. 


with  a  quivering,  jerking  motion  ;  this  is  doubtless  the 
nutrient  fluid  conveying  the  products  of  digestion  to  every 
part  of  the  common  structure. 

Where  the  branches  issue  from  the  angles  of  the  stem, 

the  medulla,  and  consequent- 
ly the  horny  sheath,  is  di- 
lated into  a  knob  ;  immedi- 
ately above  this  there  is  a 
joint-like  constriction  in  the 
tube,  and  the  branch  itself 
is  insected  by  four  or  five 
such  constrictions,  so  as  to 
form  as  many  rings.  Its  ex- 
tremity then  expands  into  an 
elegant  cup,  or  vase,  of  ex- 
treme tenuity  and  trans- 
parency, shaped  like  a  wine- 
glas  s ,  with  the  rim  undivided , 
but  so  thin  and  subtle  as  to 
be  seen  with  the  greatest 
difficulty. 

These  cups,  or  cells,  are 
each  the  proper  habitation 
of  a  polype,  which  is  nothing 
else  but  the  termination  (in  this  direction)  of  the  living, 
growing,  vascular  pith.  The  latter  becomes  exceedingly 
attenuated  in  order  to  pass  through  a  very  narrow  orifice 
in  the  centre  of  a  horny  diaphragm,  or  sort  of  false  bottom, 
which  passes  across  the  bottom  of  each  cell.  It  then 
dilates  into  a  soft,  contractile  animal,  whose  body — but 
look  for  yourself ;  for  here,  full  in  the  field  of  the  micro- 
scope, is  one  expanding  in  the  highest  vigour  and  beauty. 
It  is  a  long  trumpet-shaped  body  of  granular  flesh,  the 
mouth  of  which  just  reaches  the  brim  of  the  cup,  over 
which  it  spreads  on  all  sides.  From  its  margin  spring 
some  eighteen  or  twenty  tentacles — the  exact  number 


LAOMEDEA. 


ZOOPHYTES. 


329 


varying  in  different  individuals— arranged  in  one  or  two 
close-set  circles,  like  a  crown.  These  organs,  which,  as 
you  see,  fall  into  elegant  double  curves,  like  the  branches 
of  a  chandelier,  are  roughened  with  knobbed  rings,  some- 
thing like  the  horns  of  a  goat ;  this  structure  we  will  pre- 
sently submit  to  more  close  examination. 

In  the  midst  of  the  space  surrounded  by  the  tentacular 
crown  there  is  protruded,  at  the  pleasure  of  the  animal,  a 
large,  fleshy,  funnel-shaped  mouth,  the  lips  of  which  are 
highly  sensitive,  continually  changing  their  form;  pro- 
truding, contracting,  bending  in  upon  themselves,  now 
closing,  now  opening  the  mouth,  and,  as  it  were,  testing 
the  immediate  vicinity,  like  a  very  delicate  organ  of  some 
unknown  sense. 

The  whole  polype  is  much  too  minute  for  us  to  attempt, 
with  any  probability  of  success,  the  amputation  of  one  of 
the  tentacles  with  scissors.  But  by 
cutting  off  a  polype,  cell  and  all,  and 
putting  it  into  the  compressorium, 
we  may  be  able,  by  means  of  the 
graduated  pressure,  to  flatten  the 
whole,  and  thus  discern  the  gnarled 
structure  of  the  tentacles.  A  very 
high  magnifying  power  is  needed  for 
this. 

Here,  then,  we  have  one  of  the 
tentacles  flattened  between  the  glass 
plates,  but  still  retaining  its  integrity. 
We  find  that  the  thickenings  are 
similar  in  character  to  those  of  the 
tentacles  of  Sarsial  which  we  lately 

Observed.      They   are,    in   fact,    aCCU-    TKNTACLE^  OF^LAOMEDEA  ; 

mulations  of  cnida,   those   peculiar 
weapons  of  power,  which  I  shall  presently  describe  in  full ; 
but  here  they  are  symmetrically  arranged  in  single  rows, 
each  pointing  upward  and  outward. 


<?    -?1 


330  EVENINGS   AT    THE    MICROSCOPE. 

To  return  to  the  living  specimen  on  the  leaf :  you  see 
seated  in  the  angles  of  the  branches  here  and  there  elegant 
urn-shaped  cells,  larger  than  the  polype  cells,  each  with  a 
sort  of  shoulder  and  a  narrow  neck.  The  common  marrow 
passes  from  the  joint  into  the  bottom  of  these,  and  then 
extends  through  the  centre  till  it  reaches  the  mouth.  In 
some  of  the  urns  this  forms  merely  a  slender  column,  ex- 
panding at  the  mouth ;  but  in  others  it  enlarges  at  irregular 
intervals  into  large  knobs  or  masses  of  granular  flesh, 
which  are  confusedly  grouped  together,  eight  or  ten  in  one 
capsule.  This  latter  is  the  most  interesting  condition  ;  let 
us  watch  it. 

While  doing  so,  let  me  inform  you  that  these  urns  are  the 
reproductive  organs,  and  the  fleshy  masses  are  embryos  of 
peculiar  character,  which  are  developed  out  of  the  nutrient 
medulla.  The  largest  of  those  now  under  observation  is, 
as  you  see,  moving,  and  slowly  working  its  way  out  of  its 
glassy  prison.  Two  or  three  flexible  finger-like  bodies 
are  protruding  from  the  orifice  of  the  urn,  and  more 
are  joining  them:  we  see  they  are  tentacles,  protruded 
in  a  loose  bundle,  just  as  the  polype  emerges  from  the 
cell. 

It  is  a  somewhat  slow  process ;  but  at  length  the  fleshy 
mass  squeezes  itself  forth,  as  if  pushed  out  by  some  con- 
tractile force  behind ;  while  we  see  the  fluids,  carrying 
granules,  run  into  the  parts  of  the  tentacles  which  are 
already  free.  The  embryo  is  liberated. 

For  a  few  seconds  it  appears  helpless,  and  falls  through 
the  water  in  a  collapsed  state,  so  that  we  cannot  discern 
its  proper  form.  It  gives  a  spasmodic  contraction  or  two, 
feeble  at  first,  then  more  vigorous  ;  the  tentacles  lengthen, 
the  body  expands,  and — lo !  it  is  not  a  polype,  but  a 
Medusa ! 

And  now  take  your  eye  for  a  moment  from  the  micro- 
scope, and  glance  at  this  glass  jar,  in  which  the  oarweed 
with  its  colony  of  Zoophytes  has  been  standing  for  a  few 


ZOOPHYTES.  331 

hours.  Hold  it  between  your  eye  and  the  light ;  do  you  not 
see  that  the  water  is  alive  with  tiny  dancing  atoms  ?  Hun- 
dreds are  there,  playing  and  pumping  through  the  fluid 
with  a  sort  of  flapping  motion,  which,  when  you  get  one 
sidewise  in  clear  view,  will  not  fail  to  remind  you  of 
the  flagging  flight  of  some  heavy-bodied,  long-winged 
bird.  These  are  the  Medusa-shaped  progeny  of  the 
Laomedea. 

But  let  us  return  to  the  one  of  which  we  have  just  wit- 
nessed the  birth,  and  which  is  still  flapping  to  and  fro  in 
the  narrow  glass  trough.  You  see  a  pellucid  colourless 
disk  or  umbrella  of  considerable  thickness,  about  one- 
sixtieth  of  an  inch  in  diameter  in  its  average  state  of 
expansion.  Its  substance  has  a  reticular  appearance,  pro- 
bably indicating  its  cellular  texture.  Internally,  the  disk 
rises  to  a  blunt  point  in  the  centre,  whence  four  vessels 
diverge  to  opposite  points  of  the  margin.  These  form 
elevated  ribs,  the  surface  being  gradually  depressed  from 
each  to  the  centre  of  the  interspace.  Externally,  the 
centre  of  the  disk  is  produced  into  a  fleshy  peduncle, 
having  a  narrow  neck,  and  then  expanding  into  a  sort  of 
secondary  disk,  of  a  square  form,  with  the  angles  rounded. 
This  organ,  which  is  capable  of  varied,  precise,  and  ener- 
getic motions,  corresponds  to  the  peduncle  of  a  true 
Medusa,  the  angles  being  the  lips.  These  lips,  which 
correspond  in  their  direction  to  the  four  internal  ridges, 
are  very  protrusile ;  and,  when  the  little  animal  is  active,  are 
continually  being  thrust  out  in  various  directions,  some- 
times everted,  but  more  commonly  made  to  approach  each 
other  in  different  degrees  ;  sometimes  one  being  bent-in 
towards  the  centre,  sometimes  all  closing-up  around  a 
hollow  interior.  These  four  lobes,  thus  perpetually  in 
motion,  and  changing  within  certain  limits  their  form  and 
their  relation  to  each  other,  remind  one  of  the  lips  or  the 
tongues  of  more  highly  organised  animals.  The  substance 
of  this  peduncle  appears  to  be  delicately  granular;  but 


332  EVENINGS    AT    THE   MICBOSCOPE. 

there  is  a  very  manifest  tendency  to  a  fibrous  character  in 
its  texture,  the  fibres  being  directed  from  the  exterior  to- 
wards the  interior,  supposing  the  lobes  to  have  their  points 
in  contact. 

Let  us  now  look  at  the  margin  of  the  disk,  Here  are 
attached  twenty-four  slender  tentacles,  six  in  each  quad- 
rant formed  by  the  divergent  ribs,  or  radiating  canals. 
Each  tentacle  springs  from  a  thickened  bulb,  which  is 
imbedded  in  the  margin  of  the  disk ;  it  is  evidently 
tubular,  but  the  tube  is  not  wider  in  the  bulb  than  in  the 
filament.  The  general  surface  is  rough  with  projecting 
points,  which  in  some  assume  a  very  regular  spinous  ap- 
pearance, and  the  tentacle  terminates  in  a  blunt  point. 
The  discal  part  of  the  bulb  is  fringed  with  a  row  of  minute 
bead-like  spherules.  Around  the  edge  of  the  circumference 
of  the  disk,  on  the  exterior,  are  arranged  eight  beautiful 
and  conspicuous  vesicles  or  organs  for  hearing.  They  are 
placed  in  pairs,  those  of  each  pair  being  approximate,  and 
appropriated  to  each  of  the  quadrants  of  the  circle.  Each 
of  these  organs  consists  of  a  transparent  globe,  not  enve- 
loped in  the  substance  of  the  disk,  but  so  free  as  to  appear 
barely  in  contact  with  it :  it  contains  a  single  otolithe,  of 
high  refractive  power,  placed,  not  in  the  centre,  but  towards 
the  outer  side.  The  inexperienced  naturalist,  on  first 
seeing  these  organs,  would  unhesitatingly  pronounce  them 
eyes,  and  the  otolithe,  or  ear-stone,*  the  crystalline  lens. 
They  are,  however,  pretty  certainly,  rudimentary  organs  of 
hearing ;  the  crystalline  globule  or  otolithe  being  capable 
of  vibration  within  its  vesicle.  Their  exact  counterparts 
are  found  in  many  of  the  smaller  Medusae,  as  we  lately 
saw  in  the  Thaumantias. 

The  disk  is  endowed  with  an  energetic  power  of  con- 
traction, by  which  the  margin  is  diminished,  exactly  like 
that  of  a  Medusa  swimming ;  and  the  tentacles  have  also 
the  power  of  individual  motion,  though  in  general  this  is 

*  See  note  on  page  56. 


ZOOPHYTES.  833 

languid,  their  rapid  flapping  being  the  effect  of  the  con- 
traction and  expansion  of  the  disk,  whereby  the  margin  is 
moved  quickly  backwards  and  forwards,  carrying  the  ten- 
tacles with  it.  Occasionally,  however,  all  the  tentacles 
are  strongly  brought  together  at  their  tips,  with  a  twitch- 
ing, grasping  action,  like  that  of  fingers,  which  is  certainly 
independent  of  the  disk,  and  may  be  connected  with  the 
capture  of  the  prey. 

Now  every  detail  of  the  structure  here,  as  well  as  the 
general  form,  appearance,  and  habits,  agrees  with  the 
small  naked-eyed  Medusae,  so  closely  that  if  we  had  not 
witnessed  the  birth  of  the  little  creature  from  the  repro- 
ductive cell  of  a  Laomedea,  we  should  have  pronounced  it 
with  unhesitating  confidence  a  true  Acaleph.  The  pedun- 
cle, it  is  true,  seems  out  of  place,  being  on  the  outside  of 
the  dome,  instead  of  hanging  suspended  from  its  interior  ; 
but  this  difference  is  only  apparent,  and  arises  from  the 
circumstance  that  the  disk  is  reverted.  If  you  suppose 
the  edge  of  the  disk  to  be  turned  in  the  opposite  direc- 
tion, you  will  have  the  peduncle  in  its  proper  place :  the 
umbrella  in  these  specimens  is  carried  within,  and  the 
sub-umbrella  without;  an  inversion  which  is  probably 
accidental,  or,  at  least,  unimportant. 

Comparing  now  this  strange  production  of  a  Medusa  by 
a  Polype,  with  what  I  lately  told  you  of  the  production  of 
Polypes  by  a  Medusa  (as  in  the  case  of  the  lovely  little 
Turris),  you  will  have  some  acquaintance  with  the  won- 
drous phenomena  which  have  of  late  years  been  surprising 
and  interesting  naturalists,  viz.,  those  of  the  Alternation 
of  Generations  ;  in  which,  as  Chamisso,  the  first  disco- 
verer of  the  strange  facts,  observed, — "  a  mother  is  not 
like  its  daughter,  or  its  own  mother,  but  resembles  its 
sister,  its  grand- daughter,  and  its  grandmother."  The 
Polype  gives  birth  to  a  generation  of  Medusae  which  lay 
eggs,  which  develop  into  Polypes.  The  Medusa  on  the 
other  hand  lays  eggs  (gemmules),  which  develop  into 


334  EVENINGS   AT    THE    MICROSCOPE. 

Polypes,  which  at  length  divide  themselves  into  colonies 
of  Medusae.  * 

At  first  you  will  perhaps  see  nothing  remarkable  in 
another  object  which  I  collected  in  my  rock- ramble  to-day. 
A  Hermit-crab  in  an  old  Natica  shell ;  both  common 
things  enough.  Yet  look  more  narrowly.  The  greater 
portion  of  the  shell  is  not  smooth,  has  no  such  porcelain- 
like  polish  as  the  Natica  usually  has,  but  is  clothed  with  a 
sort  of  downy  nap,  a  coarse  sponginess  of  a  greyish  hue, 
splashed  with  yellowish  and  pink  tints.  The  shell  is  in- 
vested with  Hydractinia. 

We  restore  the  strange  partnership, — shell,  fleece,  and 
crab, — to  the  glass  of  sea-water ;  where  we  soon  see  the 
whole  tumbling  about  the  bottom  in  uncouth  agility. 
Assist  your  eye  with  this  pocket-lens,  and  look  again. 
The  shaggy  nap  upon  the  shell  now  bristles  with  tall 
slender  polypes,  crowded  and  erect,  like  ears  of  corn  in  a 
field. 

No  high  magnifying  power  is  necessary  to  furnish  us 
with  considerable  entertainment  from  this  populous  colony. 
The  polypes  stand  individually  nearly  half-an-inch  in 
height ;  each  consists  of  a  straight  slender  column,  sur- 
mounted by  eight  straight  rod-like  tentacles,  four  of  which 
stand  erect,  slightly  diverging,  and  the  other  four  alter- 
nating with  these  at  their  origin,  extend  horizontally  like 
the  arms  of  a  turnstile. 

The  rough  jolting  of  the  crab  over  the  stones  the  ex- 
panded polypes  bear  with  equanimity ;  they  are  used  to 

*  Since  this  work  was  published,  many  efforts  have  been  made  to 
explain,  and  to  bring  into  harmony  with  what  were  supposed  to  be  the 
laws  of  generation,  these  strange  facts,  which  seem  to  subvert  all  our 
notions  of  individuality.  Steenstrup's  phrase  is  now  by  common 
consent  abandoned  :  there  is  no  alternation  of  generation  proper. 
That  hypothesis  which  regards  the  phenomena  as  those  of  metamor- 
phosis, the  fixed  condition  (Laomedea)  being  analogous  to  the  larva, 
the  free-swimming  (Medusa)  to  the  adult,  is  one  of  the  most  plausible  ; 
but  an  attempt  to  apply  it  in  all  the  cases  shows  it  to  be  untenable. 
(See  Greene,  Ccelenterata,  p.  76). 


ZOOPHYTES.  835 

it ;  and  though  their  tentacles  wave  and  stream  hither  and 
thither,  they  are  not  retracted  on  this  account.  But  just 
touch  with  the  point  of  the  pencil  in  your  hand  any  part  of 
the  shaggy  fleece,  and  instantly  the  whole  colony  retire 
together,  as  if  by  a  common  impulse,  apparently  shrinking 
into  the  substance  of  the  shell.  Yet  they  soon  re-appear, 
one  after  another  quickly  protruding  its  closed  tentacles, 
which  are  presently  expanded  as  before. 

The  explanation  of  this  phenomenon  is,  that  the  whole 
colony  of  polypes  are  but  the  free  points,  or  feeding  mouths, 
of  a  common  living  film,  which  invests  the  shell ;  just  as 
in  Laomedea,  the  polypes  that  inhabit  the  vase-like  cells 
are  the  off-shoots  or  free  points  of  the  common  medulla. 

The  investing  film  will  sometimes  in  captivity  spread 
upon  the  glass  side  of  a  tank,  and  there  develop  all  the 
polypes  and  organs  proper  to  the  complete  organism. 
When  this  is  the  case,  an  admirable  opportunity  is  pre- 
sented for  studying  with  ease  and  precision  the  economy 
of  the  creature ;  and  it  is  to  the  skill  with  which  Dr.  T. 
Strethill  Wright  has  availed  himself  of  such  an  oppor- 
tunity* that  I  am  indebted  for  the  chief  part  of  the  facts 
that  I  am  going  to  tell  you,  connected  with  the  form  and 
appearance,  of  which  you  can  here  judge  for  yourself. 

The  spreading  film  or  polypary  is  a  thin  coat  of  trans- 
parent jelly,  slightly  coloured  with  various  tints,  which 
secretes  and  deposits  within  its  substance  a  still  thinner 
horny  layer  of  chitine.  This  rises  here  and  there  into 
numerous  spines  and  points,  which  are  curiously  ridged 
with  toothed  keels ;  and  these  ridges  run  in  various  direc- 
tions over  the  horny  layer  also,  making  a  fine  network  over 
it.  The  investing  flesh,  however,  fills  up  all  the  cavities 
and  areas  so  inclosed. 

The  mode  in  which  the  polypary  increases  is  by  throw- 
ing out  from  its  edge  a  creeping  band,  exactly  analogous  to 
the   root-thread   of    the   Laomedea.     This    "  propagative 
*  See  "  Edin.  New  Philosophical  Journal,"  for  April,  1857. 


386  EVENINGS   AT   THE   MICROSCOPE. 

stolon,  after  leaving  the  point  of  its  origin,  increases 
rapidly  in  diameter,  and  sends  out  irregular  branches. 
The  tips  of  these  branches  are  covered  with  a  glutinous 
cement,  by  which  they  attach  themselves  tenaciously  to 
glass,  or  other  surface  near  them.  Having  attached  them- 
selves, they  expand  laterally,  at  the  same  time  throwing 
out  finger-like  prolongations,  which,  as  they  come  in  con- 
tact with  each  other,  coalesce,  until  a  fleshy  plate  is  found 
adherent  to  the  glass.  Polypes  are  developed  both  from 
the  loose  branches  and  the  attached  polypary;  and  the 
latter  is  clearly  seen  to  be  permeated  by  a  beautiful  system 
of  anastomosing  canals,  connected  with  the  hollow  bodies 
of  the  polypes.  Within  these  canals  may  be  detected  an 
intermittent  flow  of  fluid,  containing  particles,  the  dancing 
motion  of  which  indicates  the  presence  of  ciliary  action, 
and  which,  having  passed  in  one  direction  for  a  short  time, 
are  arrested,  and,  after  a  slight  period  of  oscillation,  com- 
mence to  flow  in  an  opposite  direction." 

The  polypes  which  are  developed  from  this  living  carpet 
are  not  all  of  the  same  form.  No  fewer  than  five  distinct 
sorts  exist,  at  one  and  the  same  time ;  and  I  doubt  not  we 
shall  be  able  to  find  and  to  identify  them  all,  on  this  well- 
grown  specimen. 

First,  there  are  the  alimentary  polypes,  which  we  have 
already  cursorily  glanced  at.  Within  the  space  inclosed 
by  the  two  circles  of  tentacles,  there  is  a  mouth  with  soft 
protrusile  lips,  which  can  be  pushed  out  and  folded  back, 
so  as  to  hide  tentacles,  column,  and  all. 

Scattered  amongst  these  we  see  numerous  polypes, 
which  agree  in  general  form  with  these,  but  with  some 
remarkable  subtractions  and  additions.  They  have  no 
mouth  nor  stomach,  and  the  tentacles  are  reduced  to  the 
smallest  possible  warts  or  protuberances  like  small  teeth 
On  the  dilated  tip.  But  the  additions  are  still  more 
peculiar.  From  the  middle  part  of  the  column  a  number, 
from  four  to  nine,  of  great  oval  sacs  project,  each  attached 


ZOOPHYTES.  837 

by  one  end,  while  the  other  stretches  out  horizontally, 
thus  surrounding  the  slender  column.  Each  of  these  sacs 
is  an  ovarian  capsule,  and  contains  several  ova  of  a  bril- 
liant yellow  or  crimson  hue.  Thus  we  have  the  second 
form,  that  of  the  reproductive  polypes. 

In  some  places  single  ovarian  capsules  stand  up  alone 
from  the  fleshy  carpet,  agreeing  in  every  respect  with 
those  which  we  have  just  examined,  except  that  they  are 
sessile,  instead  of  being  carried  by  a  polype. 

The  fourth  form  is  that  of  the  tentacular  polype.  Here 
and  there,  from  amidst  the  forest  of  shorter  polypes,  both 
alimentary  and  reproductive,  white  threads  are  seen  pro- 
truding, which  extend  to  a  length  four  or  five  times  as 
great  as  theirs,  and  hang  down  or  loosely  float  in  the 
water.  They  are  found  on  the  outskirts  of  the  whole 
compound  structure,  and  at  each  extremity  of  the  long 
diameter  of  the  mouth  of  the  supporting  shell,  so  that 
they  must,  in  their  natural  condition,  reach  to  the  ground, 
along  which  the  crab-tenanted  shell  is  carried,  enabling 
the  Zoophyte  to  seize  and  appropriate  the  atoms  scattered 
by  the  crab  whenever  he  takes  his  meals.  The  tips  of 
these  organs  are  covered  with  a  dense  pavement  of  large 
thread-cells ;  and  they  must  doubtless  perform  the  office 
of  general  purveyors  to  the  composite  animal. 

But  still  more  remarkable,  more  extraordinary  than  all 
we  have  been  considering,  are  the  objects  which  are  now 
in  view  in  the  field  of  the  microscope.  You  see  a  number 
of  bodies,  which  Dr.  Wright  calls  ophidian  or  spiral 
polypes,  and  which,  as  he  truly  observes,  are  "  like  small 
white  snakes,  closely  coiled  in  one,  two,  or  three  spirals, 
and  grouped  immediately  round  the  mouth  of  the  shell." 
The  habits  of  these  polypes  are  still  stranger  than  their 
forms.  "  When  touched  they  only  draw  their  folds  more 
closely  together.  But  if  any  part  of  the  polypary,  however 
distant  from  them,  be  irritated,  the  spiral  polypes  uncoil, 
extend,  and  lash  themselves  violently  backwards  and  for- 


338  EVENINGS   AT    THE   MICROSCOPE. 

wards,  and  then  quickly  roll  themselves  up  again ;  and 
that  not  irregularly  or  independently  of  each  other,  but  all 
together,  and  in  the  same  direction,  as  if  moved  by  a 
single  spring.  A  violent  laceration  of  the  polypary  causes 
these  polypes  to  remain  extended  and  stretched  like  a 
waving  and  tremulous  fringe  across  the  mouth  of  the  shell, 
for  several  minutes.  The  ophidian  polypes  (evidently  a 
barren  modification  of  the  reproductive  polype)  are  never 
found  in  any  other  situation  on  the  polypary  than  in  that 
before  described,  or  round  the  margins  of  accidental  holes 
in  the  shell.  They  have  no  mouth,  and  the  tentacles  are 
rudimentary.  The  walls  of  the  body  are  very  transparent, 
from  the  extreme  vacuolation  of  the  inner  tissue.  The 
muscular  coat,  as  might  be  expected  from  the  active  move- 
ments of  the  polypes,  is  highly  developed,  and  forms  a 
beautiful  object  on  the  dark  polarised  field  of  the  micro- 
scope, each  spiral  coil  shining  out  as  a  bright  double  ring, 
divided  by  four  dark  sectors.  The  outer  tissue  of  the 
whole  body  and  tentacles  is  crowded  with  the  larger  thread- 
cells.  The  ophidian  polypes  are,  doubtless,  organs  of 
defence  or  offence,  like  the  motile  spines  and  bird's  head 
processes  of  the  Polyzoa,  or  the  pedicellarias  of  the  Echi- 
nodermata;  but  it  is  difficult  to  assign  a  reason  for  their 
peculiar  situation.  They  vary  much  in  number  and  size 
in  different  specimens  of  Hydractinia,  but  are  rarely  alto- 
gether absent."  * 

The  reflections .  of  the  able  zoologist  who  first  called 
attention  to  these  varied  developments,  and  his  compari- 
sons of  them  with  those  of  another  polype-form  which  we 
have  lately  been  observing,  are  so  interesting  and  instruc- 
tive that  you  will  not  deem  it  needful  that  I  should 
apologise  for  citing  them.  "In  our  consideration  of  the 
Hydractinia,"  he  observes,  "our  attention  is  arrested  by 
the  multitude  of  objects  grouped  together  to  constitute  a 
single  animal,  their  variety  in  form,  and  the  sympathy 
*  Dr.  Wright,  op.  cit. 


ZOOPHYTES.  339 

which  subsists  between  the  different  parts.  The  singular 
spinous  skeleton  ;  the  expanded  membrane  of  the  polypary, 
with  its  beautiful  internal  network  of  tubes  and  delicate 
peripheric  prolongations  ;  the  alimentary  polypes,  some 
white  and  filiform,  others  thick,  fleshy,  crimson,  or  yellow 
sacs,  obligingly  everted,  to  expose  their  interior  to  our 
microscopic  eye;  the  reproductive  polypes,  with  their 
richly  coloured  generative  sacs  ;  the  sessile  generative 
organs  of  the  polypary  ;  the  ophidian  polypes,  coiled  in  neat 
spirals  when  at  rest,  but  starting  into  furious  action,  like  a 
row  of  well-drilled  soldiers,  when  injury  is  inflicted  on  the 
body  to  which  they  are  attached  ;  and,  lastly,  the  tentacle 
polypes,  floating  in  the  water  like  long  and  slender  threads 
of  gossamer,  or  dragging  up  heavy  loads  of  food  for  the 
common  good  ;  —  these,  together  with  the  intimate  relation 
and  sympathy  subsisting  between  the  polypary  and  its 
associated  organs,  all  combine  to  form  an  object  of  the 
highest  interest,  and  indicate  that,  in  this  fixed  yet  travel- 
ling zoophyte,  we  have  a  type  of  structure  transitional 
between  the  dentritic  Hydroida  and  the  more  highly 
organised  Acaleph.*  In  the  simplest  acalephoid  form, 
such  as  the  medusoid  of  Companularia  [or  Laomedea] 
(which  is  nothing  more  than  an  extension  of  the  polypary 
specially  organised  for  independent  and  motile  life),  we 
have  (as  in  Hydractinia)  an  expanded  polpary,  repre- 
sented by  the  umbrella,  and  permeated  by  vascular  tubes, 
from  the  confluence  of  which  last  spring,  at  the  centre, 
the  tentacular  polypes,  various  in  number  ;  and  between 
them  the  reproductive  polypes,  represented  by  the  sessile 
generative  sacs."  f 

You  see  here  a  jar,  on  the  glass  side  of  which  are  traced 
a  number  of  very  fine  white  lines,  barely  discernible  by 


*  From  the  Greek  oxoA^ij  (akalephe),  a  nettle,  applied  to  animals 
known  under  the  common  name  vt  jelly-fishes  and  sea-nettles,  from  their 
causing  the  sensation  of  stinging  when  handled. 

t  Dr.  Wright,  op.  cit. 

z  2 


340  EVENINGS   AT    THE    MICROSCOPE. 

the  unassisted  eye.  But  by  the  aid  of  the  lens  you  see 
that  each  line  is  a  long  and  slender  thread,  which  creeps 
along  the  glass,  and  at  length  starts  out  from  it  free  for  a 
short  distance,  and  is  then  terminated  by  a  long  club- 
shaped  body,  which  carries  at  its  extremity  four  horizon- 
tally divergent  organs,  like  the  arms  of  a  turnstile.  Tracing 
down  the  threads  to  their  lower  extremities,  you  see  that 
they  are  branches  of  one  thread,  which  creeps  irregularly 
over  a  filamentous  sea-weed  growing  from  a  stone  in  the 
jar.  The  sea- weed  had  been  in  the  vessel  for  several 
weeks,  and  the  water  having  been  undisturbed,  the  knobbed 
thread,  which  was  originally  confined  to  the  plant,  con- 
tinued to  grow,  and,  coming  into  contact  with  the  glass, 
spread  upon  it.  Many  other  threads  have  extended  from 
the  creeping  root,  some  of  which  stand  up  freely  in  the 
water,  with  their  knobbed  extremities  floating  in  the 
wave. 

This  is  one  of  the  Polype  tribe,  named  Stauridia  pro- 
ducta,  and  as  its  form  and  structure  are  interesting,  we 
will  devote  a  few  moments  to  its  examination.  We  can 
easily  sever  one  or  two  of  the  freely  floating  threads,  and 
transfer  the  amputated  portions  to  one  of  the  live  boxes  of 
the  microscope.  The  motions  and  appearance  of  the  club 
with  its  organs  will  be,  for  a  while,  little  affected  by  the 
violence. 

The  long  cylindrical  thread  is  enveloped  in  a  transparent 
horny  tube,  which,  however,  so  closely  invests  it,  that  it 
is  with  difficulty  distinguished.  The  club-shaped  head,  or 
individual  polype,  is  an  enlargement  of  the  thread,  which 
protrudes  from  the  investing  tube.  It  is  swollen  in  the 
middle  and  rounded  at  the  end,  and  many  of  the  heads, 
which  are  more  ventricose  than  the  rest,  contain  a  bubble 
of  air  in  the  centre.  This  air  is  doubtless  taken  in  at  the 
mouth,  which  is  situated  at  the  extremity;  for,  though 
you  can  discern  no  perforation,  yet  there  is  an  aperture 
capable  of  being  opened  widely  at  the  pleasure  of  the 


ZOOPHYTES.  341 

animal,  and  surrounded  by  protrasile,  contractile,  and 
expansile  fleshy  lips.  I  have  several  times  seen  this 
mouth  opened,  and  partly  turned  outwards,  in  kindred 
species;  and  once  I  had  an  opportunity  of  witnessing  a 
quite  unexpected  use  to  which  it  was  applied,  viz.,  that  of 
a  great  sucking  disk.  I  had  put  the  animal  in  such  a 
live-box  as  this — the  two  glass  surfaces  being  just  suffi- 
ciently wide  apart  to  allow  it  free  liberty  to  turn  about  in 
all  directions  as  far  as  it  wished.  On  my  looking  at  it 
after  a  momentary  interval,  I  saw  that  the  extremity  had 
suddenly  become  a  large  circular  disk  of  thrice  the  dia- 
meter of  the  body :  its  substance  was  gelatinous,  full  of 
granules,  arranged  concentrically.  I  neither  saw  this  disk 
evolved  nor  retracted  ;  but  after  some  time,  on  looking  at 
it,  the  same  phenomenon  was  repeated.  In  order  to  ob- 
tain a  better  sight  of  it,  but  without  suspicion  of  what  I 
was  about  to  effect,  I  slightly  turned  the  tube  of  the  box, 
carrying  with  it  the  sea-weed  to  which  the  polype  was 
attached,  my  eye  upon  it  attentively  observing  all  the 
time.  The  base  of  the  polype  moved  away  from  its  posi- 
tion, but  the  broad  disk  was  immovable.  I  continued  to 
turn  the  upper  glass,  until  at  length  the  body  was  dragged 
out  so  as  to  be  considerably  attenuated  ;  still  the  disk 
maintained  its  hold  on  the  lower  glass,  with  no  other 
change  than  that  of  being  elongated  in  the  direction  in 
which  it  was  dragged.  At  length  it  slowly  gave  way,  and 
resumed  its  original  shape  by  gradual  and  almost  imper- 
ceptible diminution  of  the  circumference. 

Around  this  expansile,  but  now  fast  closed  mouth,  you 
observe  four  tentacles,  radiating  in  a  plane  at  right  angles 
to  the  axis  of  the  thread,  towards  the  four  cardinal  points; 
they  are  long,  slender,  straight,  and  each  is  terminated 
by  a  globose  head  of  considerable  size,  resembling  the 
arms  of  certain  screw-presses,  which  are  loaded  with  ter- 
minal globes  of  metal  to  increase  their  impetus  when 
turned. 


842  EVENINGS   AT   THE    MICBOSCOPE. 

The  structure   of  these  tentacles  is  very  interesting. 

The  stem  contains  .a  core 
or  central  chain  of  large 
cells,  which  take  a  some- 
!what  square  outline  from 
mutual  pressure.  The  sur- 
face is  roughened  with 
small  swellings,  from  each 
of  which  projects  a  long 
and  extremely  attenuated 
hair  (palpocil),  which  is 
probably  a  very  delicate 
organ  of  touch.  The  ter- 
minal globe  is  filled  with 
proportionately  large  oval 
vesicles,  each  with  a  cen- 
tral cavity,  which  are 
arranged  in  a  divergent 
manner  around  the  centre, 
so  that  their  tips  shall 
reach  the  surface  of  the  globe ;  these  are  those  potent 
weapons  of  offence  called  thread-cells  (cnidce).  The  sur- 
face of  the  globe  is  covered  with  short  thick  palpocils, 
which  Dr.  T.  S.  Wright  considers  as  prehensile  organs. 
"  These  palpocils  arise,  each  as  a  somewhat  rigid  process, 
from  the  side  of  one  of  the  large  thread-cells,  buried  in  the 
head  of  the  tentacle ;  and  they  probably  convey  an  im- 
pression, from  bodies  coming  into  contact  with  them,  to 
the  thread-cell,  causing  the  extrusion  of  its  duct." 

Besides  these  globe-headed  tentacles,  there  are,  on  the 
lower  part  of  the  club-foot,  four  other  organs  similar  in 
every  respect,  except  that  they  are  not  furnished  with 
heads,  nor  any  terminal  dilatation  whatever.  They  pro- 
ject horizontally  as  the  knobbed  ones,  but  their  origin, 
and  the  respective  lines  of  their  radiation,  are  intermediate 
or  alternate ;  in  other  words,  if  we  consider  the  globe- 


STAUEIDIA. 


ZOOPHYTES.  343 

heads  as  pointing  N.,  E.,  S.,  and  W.,  the  simple  ones 
point  N.E.,  S.E.,  S.W.,  and  N.W. 

From  the  carefully  made  observations  of  several  excel- 
lent naturalists,  as  Dujardin,  Steenstrup,  Dalyell,  Loven, 
and  others,  it  appears  that  this  beautiful  and  elegant  little 
Polype  gives  birth  to  medusa-shaped  young.  Contrary, 
however,  to  the  rule  in  Laomedea,  the  Medusa  is  in  this 
case  pushed  forth  as  a  bud  from  the  side  of  the  club, 
without  any  protecting  capsule.  The  process  is  exceed- 
ingly like  a  plant  developing  a  flower ;  for  the  bud  grows 
until  it  at  length  .  expands  blossom-like,  and  a  beautiful 
little  umbrella-form  Medusa  is  seen  adhering  to  the  Polype. 
At  length  the  brilliant  little  living  flower  becomes  de- 
tached ;  and,  after  swimming  freely  for  a  time,  discharges 
ova  or  gemmules  from  its  ovaries,  which  develop  into  a 
creeping  root-thread,  and  finally  into  the  club-headed 
threads  of  the  Stauridia. 

Some  objects  which  I  have  to  exhibit  to  you  are  alto- 
gether unique  as  to  their  appearance  ;  and,  if  you  are  not 
as  imperturbable  as  a  Stoic  philosopher  or  a  Mohawk 
Indian,  will  certainly  excite  both  your  risibility  and  your 
wonder.  For  some  little  time  I  have  been  keeping  in  this 
tank  a  specimen  of  that  rather  rare  and  very  interesting 
Sabella,  the  Amphitrite  vesiculosa  of  Montagu.*  You  see 
it  is  a  worm,  inhabiting  a  sort  of  skinny  tube,  much 
begrimed  with  mud,  about  two  inches  of  its  length  being 
exposed;  the  remainder,  or  about  as  much  more,  being 
concealed  among  the  sand  and  sediment  of  the  bottom. 

A  beautiful  object  is  presented  by  the  gill-fans  of  this 
worm.  These  organs  are  always  elegant,  whatever  species 
of  the  genus  is  before  us ;  but  here,  in  addition  to  the 
charm  of  the  slender  filaments,  so  delicately  fringed  with 
their  double  comb-like  rows  of  cirri,  the  tip  of  each  bears 
a  dark  purple  spherule.  That  of  the  anterior  filament  on 
each  side  is  much  larger  than  the  rest,  and  forms  a  stout, 
*  "Linn.  Trans.,"  xi.  19. 


344  EVENINGS   AT    THE    MICROSCOPE. 

globose,  nearly  black  ball ;  tlie  others  diminish  to  about 
the  twelfth  on  each  side,  where  they  disappear.  These 
balls  are  placed  on  the  inner  or  upper  face  of  the  filament- 
stem,  at  the  point  where  the  pectination  ceases,  the  stem 
itself  being  continued  to  a  slender  point  beyond  it,  and 
constituting  the  "  short  hyaline  appendage  "  of  Montagu. 
From  their  great  resemblance  to  the  tentacle-eyes  of  the 
Gasteropod  Mollusca,  I  have  little  doubt  that  these  are 
organs  of  vision.  If  so,  the  profusion  with  which  the 
Sabella  is  furnished  in  this  respect  may  account  for  its 
excessive  vigilance ;  which  is  so  great,  that  not  only  will 
the  intervention  of  any  substance  between  it  and  the  light 
cause  it  to  retire,  but  very  frequently  it  will  dart  back  into 
its  tube  almost  as  soon  as  I  enter  the  room,  even  while  I 
am  ten  feet  distant. 

It  is  not,  however,  to  the  tube,  nor  to  the  worm,  that  I 
wish  specially  to  direct  your  attention  :  yet  it  is  necessary 
that  I  say  a  preliminary  word  about  the  former.  Ordi- 
narily the  tubes  of  these  worms  are  formed  of  the  fine 
impalpable  earthy  matters  (clay,  mud,  &c.)  held  in  sus- 
pension in  the  sea,  incorporated  with  a  chitinous  secretion 
from  the  body  of  the  animal ;  and  therefore  the  surface  of 
the  tube  is  always  rough  and  opaque.  But  in  this  indivi- 
dual case,  the  water  in  the  vessel,  probably  owing  to  its 
habitual  stillness,  not  holding  in  suspension  the  particles 
of  mud  that  ordinarily  enter  into  the  composition  of  the 
tube,  the  latest  formed  portion  is  composed  of  pure  trans- 
parent chitine,  without  any  perceptible  earthy  •  element. 
This  clear  terminal  portion  of  the  tube  you  may  perceive 
to  be  occupied  by  a  curious  parasite.  About  twenty  bodies, 
having  a  most  ludicrously- close  resemblance  to  the  human 
figure,  and  as  closely  imitating  certain  human  motions,  are 
seen  standing  erect  around  the  mouth  of  the  tube,  now 
that  the  Sabella  has  retired  into  the  interior,  and  are  in- 
cessantly bowing  and  tossing  about  their  arms  in  the  most 
energetic  manner. 


ZOOPHYTES.  345 

As  soon  as  you  have  recovered  a  little  from  your  sur- 
prise at  this  strange  display,  we  will  begin  to  examine  the 
performers  more  in  detail.  A  slender  creeping  thread, 
irregularly  crossing  and  anastomosing,  so  as  to  form  a 
loose  network  of  about  three  meshes  in  width,  surrounds 
the  margin  of  the  SabellcCs  tube,  adhering  firmly  to  its 
exterior  surface,  in  the  chitinous  substance  of  which  it 
seems  imbedded.  Here  and  there  free  buds  are  given  off, 
especially  from  the  lower  edge  ;  while  from  the  upper 
threads  spring  the  strange  forms  that  have  attracted  our 
notice.  These  are  spindle-shaped  bodies,  about  ^th  of 


an  inch  in  height,  whose  lower  extremities  are  of  no 
greater  thickness  than  the  thread  from  which  they  spring  ; 
with  a  head-like  lobe  at  the  summit,  separated  from  the 
body  by  a  constriction,  immediately  below  which  two 
lengthened  arms  project  in  a  direction  towards  the  axis  of 
the  tube. 

Such  is  the  external  form  of  these  animals,  and  their 
movements  are  still  more  extraordinary.  The  head-lobe 
of  each  one  moves  to  and  fro  freely  on  the  neck,  the  body 
sways  from  side  to  side,  but  still  more  vigorously  back- 
ward and  forward,  frequently  bending  into  an  arch  in 
either  direction  ;  while  the  long  arms  are  widely  expanded, 


346  EVENINGS   AT    THE    MICROSCOPE. 

tossed  wildly  upward,  and  then  waved  downward,  as  if  to 
mimic  the  actions  of  the  most  tumultuous  human  passion. 

"Whenever  the  Sabella  protrudes  from  its  tube,  these 
guardian  forms  are  pushed  out,  and  remain  nearly  in  con- 
tact with  the  Annelid's  body,  moving  but  slightly ;  but  no 
sooner  does  it  retire  than  they  begin  instantly  to  bow  for- 
ward and  gesticulate  as  before.  These  movements  are 
continued,  so  far  as  I  have  observed,  all  the  time  that  the 
SabeUa  is  retracted,  and  are  not  in  any  degree  dependent 
on  currents  in  the  surrounding  water,  whether  those  cur- 
rents be  produced  by  the  action  of  the  Annelid  or  by  other 
causes.  They  are  not  rhythmical ;  each  individual  ap- 
pears to  be  animated  by  a  distinct  volition. 

Applying  a  higher  magnifying  power  than  we  have  yet 
used  to  the  animals,  we  find  that  the  head-lobe  incloses  a 
central  cavity ;  that  the  arms  are  also  hollow,  with  thick 
walls,  marked  with  transverse  lines,  indicating  flattened 
cells,  and  muricated  on  the  exterior ;  and  that  the  body 
contains  an  undefined  somewhat  opaque  nucleus,  doubtless 
a  stomachal  cavity. 

I  cut  out,  with  fine  scissors,  a  segment  of  the  tube,  in- 
cluding two  of  the  parasites,  with  the  portion  of  the  net- 
work of  threads  that  carried  them.  They  have  become 
immediately  paralysed  by  the  division  of  the  threads,  but 
those  that  remain  on  the  tube  are  unaffected  by  the 
violence.  Subjecting  one  of  the  animals  so  cut  out  to  the 
action  of  the  compressorium,  with  a  power  of  560  dia- 
meters, the  arms  are  seen  to  be  formed  of  globose  cells, 
made  slightly  polyhedral,  or  many-sided,  by  mutual  pres- 
sure, set  in  single  series.  The  interior  of  these  organs  is 
divided  by  partitions,  placed  at  intervals  of  about  the  dia- 
meter. Some  at  least  of  the  cells  contain  a  small  bright 
eccentric  nucleus. 

When  the  tissues  were  quite  crushed  down  by  the  pres- 
sure of  the  compressorium,  a  quivering  motion  was  visible 
among  the  disjointed  granules,  but  it  was  very  slight.  No 


ZOOPHYTES.  347 

trace  of  cilia,  nor  any  appearance  of  ciliary  motion,  was 
perceptible  during  life. 

When  I  first  discovered  these  strange  beings,  I  was  as 
much  astonished  by  what  I  saw  as  you  are ;  nor  could  I 
imagine  to  what  class  of  animals  they  were  to  be  referred. 
Neither  did  I  know  whether  their  presence  on  the  tube  of 
the  worm  was  a  mere  accident,  or  whether  it  indicated  a 
predominant  instinct.  On  both  these  points,  however, 
light  has  been  shed. 

This  larger  Sabella  tube  was  not  the  only  one  infested 
with  the  parasites.  I  observed  them  on  at  least  two 
smaller  specimens  of  the  same  species,  in  the  same  situa- 
tion, and  with  precisely  the  same  movements.  The  ex- 
tremity of  one  of  these  smaller  tubes  I  cut  wholly  off,  and 
placed  in  the  live-box  of  the  microscope.  Two  of  the 
parasites  only  were  on  it,  which  were  active  at  first,  but 
in  about  an  hour — probably  from  the  exhaustion  of  the 
oxygen  in  the  small  quantity  of  water  inclosed — they  de- 
composed, or  rather  disintegrated,  the  outline  dissolving, 
and  the  external  cells  becoming  loose  and  ragged,  and  the 
whole  animal  losing  its  definite  form. 

One  of  these  specimens,  however,  while  yet  alive  and 
active,  afforded  me  an  observation  of  value.  I  had  already 
associated  the  form  conjecturally  with  the  Hydroid  Polypes, 
and  was  inclined  to  place  it  in  the  family  Corynida,  con- 
sidering the  arms  to  be  tentacles,  and  the  head-lobe  to  be 
homologous  with  them  in  character,  but  abnormal  in  form. 
It  appeared  to  be  a  three-tentacled  Coryne,  with  the  ten- 
tacles simple  instead  of  having  heads.  But  while  I  was 
observing  the  individual  in  question,  I  saw  it  suddenly 
open  the  head-lobe,  and  unfold  it  into  the  form  of  a  broad 
shovel-shaped  expanded  disk,  not  however  flat,  but  with 
the  two  halves  inclining  towards  each  other,  like  two 
leaves  of  a  half-opened  book.  This  immediately  reminded 
me  of  the  great  sucking-disk  which,  as  I  lately  told  you,  I  had 
seen  evolved  from  the  obtuse  summit  of  Stauridia  producta, 


348  EVENINGS  AT    THE    MICEOSCOPE. 

and  confirmed  my  suggestion  of  the  natural  affinities  of 
the  form. 

Altogether  unlike,  in  their  shape,  and  in  the  unwonted 
vivacity  and  peculiar  human  character  of  their  movements, 
all  the  other  members  of  their  natural  family  that  I  had 
ever  seen  or  heard  of,  these  curious  creatures  have  afforded 
much  entertainment,  not  only  to  myself,  but  to  those 
scientific  friends  to  whom  I  have  had  opportunities  of 
exhibiting  them.  When  I  see  them  surrounding  the  man- 
sion of  the  Sabella,  gazing,  as  it  were,  after  him  as  he 
retreats  into  his  castle,  flinging  their  wild  arms  over  its 
entrance,  and  keeping  watch  with  untiring  vigilance  until 
he  reappears,  it  seems  to  require  no  very  vivid  fancy  to 
imagine  them  so  many  guardian  demons ;  and  the  Lares 
of  the  old  Roman  mythology  occurring  to  memory,  I  de- 
scribed the  form  under  the  scientific  appellation  of  Lar 
Sabellarum.  You  may,  however,  if  it  pleases  you  better, 
call  them  "  witches  dancing  round  the  charmed  pot."* 

The  Polypes  that  we  have  as  yet  been  looking  at  are  all 
of  simple  structure  individually,  though  some  of  them  we 
have  seen  united  into  a  very  populous  community  of  com- 
pound life.  We  will  now  look  at  some  whose  organisation 
is  of  a  higher,  that  is,  more  complex  character. 

On  this  old  worm-eaten  oyster  shell,  which  has  been 
dredged  up  from  the  bottom  of  the  sea,  you  observe 
several  rounded  lumps.  They  are  of  a  cream-white  hue, 
of  somewhat  solid  texture,  tough  and  hard  to  the  touch, 
and  studded  all  over  with  shallow  depressions  or  pittings. 
The  largest  of  these  is  not  more  than  an  inch  and  a-half  in 
height,  by  two-thirds  of  an  inch  in  thickness ;  but  specimens 
often  occur  of  twice  or  thrice  these  dimensions,  and  much 

*  Since  my  first  discovery  of  this  strange  form  in  1855,  and  my 
memoir  on  it  in  the  "  Trans,  of  the  Linnean  Society,"  it  has  remained 
unrecognised  (and,  indeed,  somewhat  suspected)  for  seventeen  years. 
In  the  summer  of  1872,  however,  it  again  occurred  to  the  observation 
of  the  Rev.  T.  Hincks,  who  published  a  paper,  with  illustrations,  on  it, 
in  the  Annals  and  Mag.  of  Nat.  Hist,  for  Nov.,  1872. 


ZOOPHYTES.  349 

more  divided  than  this ;  sometimes  forming  a  rude  re- 
semblance to  a  hand  of  stumpy,  round  fingers  of  sodden 
flesh  ;  whence  the  fishermen  call  the  object  "  Dead  men's 
fingers,"  or  sometimes,  by  a  comparison  equally  apt, 
"  Cow's  paps."  To  zoologists  it  is  known  as  Atcyonium 
digitatum. 

Certainly  there  is  nothing  very  attractive  in  these  white 
lumps  as  they  now  appear ;  but  then  they  are  now  in  un- 
dress ;  they  do  not  expect  to  see  company  out  of  water. 
Their  drawing-room  is  beneath  the  waves,  in  some  sub- 
merged cave  of  ocean,  where  the  sun's  ray  never  pene- 
trated, and  where  the  only  light  is  that  dim  green  haze 
reflected  from  the  sand  and  shingle  of  the  sea-floor,  save 
when,  on  gala  occasions,  perchance,  the  Laomedea  that 
fringe  the  walls  light  up  their  myriads  of  fairy  lamps,  and 
the  tiny  Medusa  crowd  into  the  watery  festivities  with 
their  elfish  circlets  and  spangles  of  living  flame.  It  is 
then  that  the  Cow's  paps  "  take  their  hair  out  of  paper," 
and  display  their  loveliness  to  advantage. 

Unfortunately,  we  have  no  card  of  invitation  to  these 
submarine  routs,  but  perhaps  we  may  induce  one  of  the 
more  juvenile  of  these  beauties  to  indulge  us,  as  a  special 
favour,  with  a  sample  of  the  effect ;  particularly  if  we  can 
improvise  a  ball-room  suited  to  the  occasion.  Let  us  try. 

Selecting  the  very  smallest  specimen — a  tiny  thing  no 
larger  than  a  pea — I  try  to  detach  it  without  injury,  by 
inserting  the  tip  of  my  pocket-knife  under  the  frilled 
lamina  of  oyster-shell  on  which  it  rests,  and  working  off 
the  fragment.  I  have  succeeded :  here  it  is,  its  attach- 
ment unbroken  :  it  is  still  firmly  adherent  to  the  severed 
slice  of  shell,  which  is  so  small  that  I  can  drop  it  with  its 
burden  into  this  narrow  trough  of  glass.  The  whole  con- 
cern— trough,  shell,  and  polype — is  now  to  be  dropped 
into  this  capacious  jar  of  freshly  dipped  sea-water,  and 
put  away  for  an  hour  into  a  dark  closet. 


350  EVENINGS   AT    THE    MICKOSCOPE. 

Now  let  us  see  the  result.  Yes,  it  is  as  I  expected. 
The  united  stimulus  of  the  darkness  and  the  sea-water 
has  acted  on  the  Cow's  pap,  just  as  would  the  rising  and 
covering  tide  in  its  native  cavern,  after  it  had  been  left 
exposed  for  some  hours  by  the  recess  of  the  sea.  It  is 
fully  expanded,  and  is  now  as  lovely  as  just  now  it  was 
unpleasing. 

In  the  first  place  it  is  swollen  to  twice  its  former  dimen- 
sions, and  has  acquired  at  the  same  time  a  semi-pellucidity, 
and  a  more  delicate  hue.  But  in  place  of  the  pits  on  the 
surface  (there  were  not  more  than  half-a-dozen  in  this 
little  specimen,  which  makes  it  more  suitable  for  examina- 
tion), it  is  covered  with  tall  polypes,  standing  out  on  all 
sides,  of  crystalline  clearness  and  starry  forms,  each  emi- 
nently beautiful  in  itself,  and  surrounding  the  whole  mass 
with  a  sort  of  atmosphere  of  almost  invisible  and  im- 
palpable lustre  peculiarly  charming. 

Coy  as  these  deep-water  strangers  are  of  displaying 
their  beauties  in  our  glaring  aquariums,  they  will  bear 
with  equanimity  a  good  deal  of  shaking,  when  once  they 
are  expanded.  Hence  I  may  be  able  to  transfer  the 
trough  with  its  contents  from  the  jar  to  the  stage  of  the 
microscope,  and  thus  enable  you  to  gaze  on  its  details  for 
a  little  while,  before  the  dull  sensorium  of  the  creature  is 
sufficiently  warned  of  its  ungenial  position  to  cause  it  to 
shut  itself  up  and  resume  its  ugliness. 

As  the  protruded  polypes  are  exactly  alike,  it  will  be 
enough  to  confine  our  attention  to  one.  It  is  an  elevated 
tubular  column  of  translucent  substance,  terminating  in  an 
expanded  flower  of  eight  slender  pointed  petals,  which 
spring  outward  with  a  graceful  swell,  so  as  to  give  the 
form  of  a  shallow  bell  to  their  general  outline.  The  base 
springs,  like  the  foot  of  a  tree,  from  the  margin  of  a  cell, 
which  penetrates  the  substance  of  the  mass,  into  which  we 
can  see  far  down,  and  into  which  the  whole  of  the  now 
extended  and  expanded  blossom  was  withdrawn  when  we 


ZOOPHYTES. 


351 


first  saw  it,  leaving  only  the  shallow  depression  to  mark 
its  situation. 

The  form  of  the  column  is  in  general  that  of  the  trunk 
of  a  tree,  or  that  of  a  long  cone  ;  but  there  is  a  sudden 
constriction  just  above  the  base,  and  another  below  the 
point,  where  what  may  be  called  the  flower  expands.  It 
is  the  petals  of  this  latter  which  constitute  the  principal 
charm  of  this  creature.  They  are,  properly  speaking,  the 
tentacles  of  the  polype,  answering  in  function  and  position 
to  those  on  the  Laomedea,  but  differing  considerably  from 
them  in  form.  Each  of  the  eight  is  thick  and  broad  at  its 


POLYPES   OP  COW'S  PAP. 


origin,  and  quickly  tapers  to  a  point :  on  each  of  two 
opposite  sides — viz.,  those  which  look  towards  the  two 
adjoining  tentacles — runs  a  row  of  delicately  slender  fila- 
ments, which  at  the  middle  part  of  the  tentacle  are  mode- 
rately long,  but  diminish  regularly  as  they  approach  either 
end.  Starting  from  the  side  of  the  tentacle,  in  the  plane 
of  its  transverse  diameter,  these  elegant  pinnas  presently 
arch  downwards,  but  with  perfect  uniformity  and  sym- 


352  EVENINGS    AT    THE    MICROSCOPE. 

metry.  By  means  of  the  high  magnifying  power  which  I 
have  now  applied,  each  of  these  pinnae  is  seen  to  be 
roughened  with  whorls  of  knobs,  which  are  accumulations 
of  cnidae,  analogous  to  those  which  we  lately  demonstrated 
in  the  tentacle  of  Laomedea. 

In  the  midst  of  the  area  surrounded  by  the  petal-like 
tentacles,  a  narrow  slit  opens  into  the  stomach.  This 
organ  is  a  flat  sac,  resembling  an  empty  pillow-case  hang- 
ing down  in  the  centre  of  the  column,  and  open  at  the 
lower  end.  From  this  end,  which  does  not  extend  to 
more  than  one-sixth  of  the  depth  of  the  cavity,  three 
threads,  much  twisted  and  irregularly  thickened,  spring 
off  at  each  side  and  arch  downwards,  for  a  short  distance. 
These  are  the  reproductive  organs,  which  fringe  the  free 
edges  of  as  many  delicate  membranes  which  run  up  as 
perpendicular  partitions  between  the  stomach  and  outer 
wall,  uniting  with  both,  and  thus  dividing  the  space  sur- 
rounding the  stomach  into  chambers  open  at  the  bottom. 
There  are  eight  of  these  septa  (as  the  partitions  are 
called),  but  one  on  each  side  is  destitute  of  the  fringing 
twisted  thread. 

The  whole  surface  of  the  interior — the  walls,  the 
stomach,  and  the  septa — is  clothed  with  fine  vibratile 
cilia,  by  the  action  of  which  constant  currents  are  main- 
tained in  the  water,  which  bathes  every  part  of  the  cavity, 
freely  entering  at  the  mouth.  We  can  distinctly  trace 
these  ciliary  currents  hurling  along  with  irregular  energy 
the  products  of  digestion,  in  the  form  of  translucent 
granules,  especially  along  the  edges  of  the  septa. 

Though  the  substance  of  the  polype  is  soft  and  flexible, 
it  contains  solid  elements.  Just  below  the  expansion  of 
the  tentacular  blossom,  we  see  imbedded  in  the  skin  a 
vast  mass  of  calcareous  needle-like  bodies  called  spicula. 
Individually,  these  are  very  minute,  and  their  form  is 
swollen  in  the  middle,  and  taper  at  each  extremity,  the 
whole  roughened  with  projecting  knots.  Collectively,  they 


ZOOPHYTES.  853 

are  grouped  in  regular  forms,  crowded  into  dense  masses 
at  the  foot  of  each  tentacle  ;  the  mass  having  a  three- 
pointed  outline,  of  which  the  central  and  largest  point 
runs  up  into  the  tentacle. 

Towards  the  lower  region  of  the  column,  spicula  again 
occur,  scattered  throughout  the  skin,  and  crowded  into 
groups,  one  on  each  interseptal  space.  These  spicula  are 
of  a  very  different  shape  from  the  upper  ones ;  for  they 
form  short  thick  cylinders,  with  each  end  dilated  into  a 
star  of  five  or  six  short  branches,  which  are  again  starred 
at  their  truncate  ends. 

If  we  now  sacrifice  our  little  Cow's  pap  to  our  scientific 


8P1CCLA   OF   COW'S   PAP. 

curiosity,  we  shall  see  something  of  its  internal  structure. 
When  removed  from  the  water,  the  flower-like  polypes 
soon  retract.  I  now  cut  open  the  mass  lengthwise  with 
a  keen  knife,  and  you  see  that  it  is  permeated  by  canals 
running  from  the  base  towards  every  part  of  the  circum- 
ference, dilating  here  and  there  to  form  the  cells  which 
protrude  and  retract  the  polypes.  This  is  a  complete  system 
of  water-supply  :  the  surrounding  sea- water,  entering  at 
the  mouths  of  the  several  polypes,  bathes  the  whole  in- 
terior, and  conveys  oxygen  and  the  products  of  digestion 
together  to  every  part  of  the  compound  organism. 

A  A 


354  EVENINGS   AT    THE    MICROSCOPE. 

The  fleshy  substance  which  surrounds  these  canals  is  of 
a  loose,  spongy  character,  and  grates  beneath  the  knife : 
a  circumstance  which  is  owing  to  the  predominance  of 
the  calcareous  element  here,  as  you  will  see  when  I  ex- 
tract a  small  portion  of  it,  and,  laying  it  on  a  slip  of 
glass,  treat  it  with  caustic  potass.  The  microscope  now 
reveals  a  large  number  of  spicula,  far  larger  than  those 
we  have  hitherto  observed,  and  different  from  either  sort 
in  form.  These  resemble  very  gnarled  branches  of  oak, 
with  the  branchlets  broken  off  close  to  their  origin,  leaving 
ragged  and  starred  ends. 


SEA- ANEMONES  :  THEIB  WEAPONS.          855 


CHAPTER  XIX. 

SEA- ANEMONES  :  THEIB  WEAPONS. 

A  VEKY  vast  amount  of  the  energy  of  animal  life  is  spent 
either  in  making  war,  or  in  resisting  or  evading  it.  Offence 
and  defence  are  sciences  which  the  inferior  creatures  can 
in  nowise  neglect,  since  all  are  interested  in  one  or  other, 
and  many  in  both ;  and  various  are  the  arts  and  devices, 
the  tricks  and  stratagems,  the  instincts  and  faculties,  em- 
ployed in  that  earnest  strife  which  never  knows  a  suspen- 
sion of  hostilities.  All  classes  of  animals,  invertebrate  as 
well  as  vertebrate,  are  warriors  by  profession :  the  Spider 
is  as  carnivorous  as  the  Lion,  and  more  strategic ;  and 
the  invisible  Brachion  is  as  ruthless  and  insatiable  as 
either. 

An  enumeration  and  description  of  the  different  kinds 
of  iceapons,  by  means  of  which  this  truceless  warfare  is 
carried  on,  would  make  a  volume :  nor  would  the  subject 
be  then  exhausted  ;  for  since  it  enters  so  largely  into  the 
very  existence  of  animal  life,  the  discoveries  of  advancing 
science  are  ever  bringing  to  light  new  forms  and  modifica- 
tions, strange  and  unexpected  contrivances,  all  calculated 
to  enhance  our  view  of  the  inexhaustible  resources  of  the 
Lord  God  Omnipotent,  "  Who  is  wonderful  in  counsel, 
and  excellent  in  working." 

I  am  going  to  bring  under  your  notice  this  evening 
some  highly  curious  examples  of  animal  weapons,  of  which 
the  very  existence  was  until  lately  altogether  unsuspected ; 
yet  so  profusely  distributed  that  they  are  eminently  cha- 
racteristic of  the  animals  we  have  been  recently  consider- 

AA2 


356  EVENINGS   AT    THE    MICROSCOPE. 

ing — viz.,  the  Medusae  and  the  Zoophytes.  They  have 
repeatedly  fallen  under  our  observation  in  examining  the 
specimens  of  these  creatures  which  we  had  selected,  but  I 
had  reserved  the  fuller  elucidation  of  them  for  an  occasion 
in  which  they  should  come  before  us  under  circumstances 
of  such  unusual  development  as  greatly  to  facilitate  our 
researches.  The  weapons  I  speak  of  are  the  cnida  or 
nettling-cells. 

Look  at  this  beautiful  Scarlet-fringed  Anemone  (Sagarta 
miniata),  expanding  to  the  utmost  its  disk  and  tentacles  in 
the  clear  water  of  the  tank.  I  touch  its  body ;  instantly 
the  blossom-like  display  is  withdrawn :  the  column  closing 
over  it  in  the  form  of  a  hemispherical  button,  which  goes 
on  contracting  spasmodically.  At  the  same  time  see  these 
white  threads  which  shoot  out  from  various  points  of  the 
surface  ;  new  ones  appearing  at  every  fresh  contraction, 
and  streaming  out  to  a  length  of  several  inches,  resem- 
bling in  appearance  fine  sewing  cotton,  twisted  and  tangled 
irregularly. 

Now  the  animal  has  attained  its  utmost  contraction,  and 
the  threads  lengthen  no  more.  But  already  they  are 
disappearing;  each  is  returning  into  the  body  by  the 
orifice  at  which  it  issued.  It  is,  as  you  may  see  by  exa- 
mining it  carefully  with  a  lens,  gradually  contracting  into 
small  irregular  coils,  at  that  end  which  is  attached  to  the 
animal ;  and  these  little  coils  are,  one  after  the  other, 
sucked-in,  as  it  were,  through  an  imperceptible  orifice. 

Before  the  whole  have  disappeared,  we  will  secure  a 
portion  for  examination.  For  this  purpose  I  cut  off  with 
sharp  scissors  about  one- sixth  of  an  inch  of  the  extremity 
of  one  of  the  threads,  which  now  I  transfer  to  a  drop 
of  sea-water  in  the  compressorium.  These  threads  are 
called  acontia. 

Examining  this  fragment  under  a  low  power  of  the 
microscope,  we  readily  see  that,  though  at  first  it  seems 
a  solid  cylinder,  it  is  really  a  flat  narrow  ribbon  with  the 


SEA- ANEMONES  :  THEIB  WEAPONS.          857 

edges  curved-in,  which  can  at  pleasure  be  brought  into 
contact,  and  thus  constitute  a  tube.  Like  all  other  internal 
organs  in  these  animals,  its  surface  is  richly  ciliated, 
and  the  ciliary  currents  not  only  hurl  along  whatever 
floating  atoms  chance  to  approach  the  surface,  but  cause 
the  detached  fragments  themselves  to  wheel  round  and 
round,  and  to  swim  away  through  the  water.  Though 
there  is  not  the  slightest  trace  of  fibre  in  the  structure  of 
the  acontium,  when  examined  even  with  a  power  of  eight 
hundred  diameters,  the  clear  jelly,  or  sarcode,  of  which 


PORTION  OF  ACONTITM  (flattened). 

its  basis  is  composed,  is  endowed  with  a  very  evident  con- 
tractility ;  the  filament  can  contract  or  elongate ;  can 
extend  itself  in  a  straight  line,  or  throw  its  length  into 
spiral  curves  and  contorted  coils ;  can  bring  its  margins 
together,  or  separate  them  in  various  degrees ;  can  per- 
form the  one  operation  at  one  part,  and  the  other  at 
another,  and  thus  can  enlarge  or  attenuate  the  general 
diameter  of  the  cord,  apparently  at  will;  and  some  of 
these  changes  can  be  effected  even  in  the  fragment  de- 


358 


EVENINGS    AT    THE    MICROSCOPE. 


tached  from  the  animal,  thus  proving  that  the  moving  power, 
whatever  it  is,  is  situated  in  the  constituent  tissue  itself. 

Under  pressure  the  edges  of  the  flattened  acontium 
appear  to  be  thronged  with  clear  viscous  globules,  over- 
lapping one  another,  and  protruding;  indicating  one  or 
more  layers  of  superficial  cells,  doubtless  forming  the 
epithelium.*  As  the  pressure  is  increased,  these  ooze 
out  as  long  pear-shaped  drops,  and  immediately  assume  a 
perfectly  globular  form,  with  a  highly  refractive  power. 
Below  these  are  packed  a  dense  crowd  of  cnida,  arranged 
transversely. 

Before  we  proceed  to  the  examination  of  these  curious 
organs  in  detail,  it  may  be  well  to  devote  a  moment's 
attention  to  the  mechanism  by 
which  the  acontia  themselves 
are  projected  from  the  body. 
As  this  was  first  described  (so 
far  as  I  am  aware)  by  myself,! 
I  will  take  the  liberty  of  citing 
some  of  my  observations  on 
the  matter. 

The  omission  of  the  acon- 
tia is  provided  for  by  the  exist- 
ence of  special  orifices,  which 
I  term  cinclides.  The  integu- 
ment of  the  body,  in  the  Sagar- 
tia,  is  perforated  by  minute 
foramina,  having  a  resemblance 
in  appearance  to  the  spiracula 
of  Insects.  They  occur  in  the 
interseptal  spaces  ;  opening  a 
communication  between  these 


CINCLIDES. 


*  The  thin,  delicate  cuticle  or  skin  which  covers  all  the  free,  un- 
inclosed,  internal  surfaces  of  the  body. 

f  In  a  memoir,  entitled  "  Researches  on  the  Poison  Apparatus  in  the 
Actiniadze,"  read  before  the  Royal  Society,  Feb.  4th,  1858. 


SEA- ANEMONES  I  THEIE  WEAPONS.         859 

(and  therefore  the  general  visceral  cavity)  and  the  external 
water.  It  follows  that  they  are  placed  in  perpendicular 
rows;  but  I  have  not  been  able  to  trace  any  other  re- 
gularity in  their  arrangement.  So  far  as  I  have  seen,  they 
are  so  scattered,  that  one,  two,  or  even  more  contiguous 
intersepts  may  be  quite  destitute  of  a  cinclis.  I  would  not, 
however,  attach  too  much  weight  to  this  negative  evidence, 
since  the  animal  has  the  power  of  closing  them  individu- 
ally at  will,  and  that  so  completely,  that  the  most  careful 
scrutiny  does  not  detect  their  presence. 

Perhaps  the  best  mode  of  examining  them  is  to  put  a 
small  specimen  of  the  8.  dianihus  or  8.  bellis  into  a  narrow 
parallel-sided  glass  cell,  filled  with  sea-water.  After  a 
while  the  animal  will  be  much  distended ;  the  exhaustion 
of  the  oxygen  impelling  the  Anemone  to  bathe  its  organs 
with  as  large  a  quantity  of  the  fluid  as  it  can  inhale.  The 
pellucidity  of  all  the  integuments  will  be  thus  greatly 
increased.  A  strong  lamp-light  being  now  reflected  by 
means  of  the  mirror  through  the  animal  on  the  stage  of 
the  microscope,  an  inch  or  a  half-inch  object-glass  will 
probably  reveal  the  orifices  in  question  with  much  dis- 
tinctness. 

The  appearance  of  the  cinclides  may  be  compared  to  that 
which  would  be  presented  by  the  lids  of  the  human  eye, 
supposing  these  to  be  reversed;  the  convexity  being 
inwards.  Each  is  an  oval  depression,  with  a  transverse 
slit  across  the  middle.  When  closed,  this  slit  may  some- 
times be  discerned  merely  as  a  dark  line — the  optical 
expression  of  the  contact  of  the  two  edges;  but,  when 
slightly  opened,  a  brilliant  line  of  light  allows  the  passage 
of  the  rays  from  the  lamp  to  the  beholder.  From  this 
condition  the  lids  may  separate  in  various  degrees,  until 
they  are  retracted  to  the  margin  of  the  oval  pit,  and  the 
whole  orifice  is  open. 

The  dimensions  of  the  cinclides  vary  not  only  with  the 
species,  and  probably  also  with  the  size  of  the  individual, 


360  EVENINGS    AT    THE    MICROSCOPE. 

but  with  the  state  of  the  muscular  contraction  of  the 
integument,  as,  also,  I  think,  with  the  pleasure  of  the 
animal.  In  a  small  specimen  of  S.  dianthus,  I  found  the 
width  of  a  cinclis,  measured  transversely,  -g^th  of  an  inch  ; 
but  that  of  another,  in  the  same  animal,  was  more  than 
twice  as  great,  viz.,  rihyth  °f  an  incn»  This  was  on  the 
thickened  marginal  ring,  or  parapet,  which  in  this  species 
surrounds  the  tentacles,  where  the  cinclides  are  larger  than 
elsewhere.  Watching  a  specimen  of  S.  nivea  under  the 
microscope,  I  saw  a  cinclis  begin  to  open,  and  gradually 
expand  till  it  was  almost  circular  in  outline,  and  ^y^th  of 
an  inch  in  diameter.  I  slightly  touched  the  animal,  and 
in  an  instant  it  enlarged  the  aperture  to  -^ih  of  an  inch. 
In  a  specimen  of  S.  bellis,  less  than  half-grown,  I  found  the 
cinclides  numerous,  and  sufficiently  easy  of  detection,  but 
rather  less  denned  than  in  dianthus  or  nivea.  They 
occurred  at  about  every  fourth  intersept,  three  intersepts 
being  blind  for  each  perforate  one  ;  and  about  three  or  four 
in  linear  series,  but  not  quite  regularly  in  either  of  these 
respects.  In  this  case  they  were  about  -^th  of  an  inch  in 
transverse  diameter — a  large  size ;  and  I  measured  one 
which  was  even  -pjtia.  of  an  inch.  By  bringing  the  animal 
before  the  window,  I  could  discern  the  light  through  the 
tiny  orifices  with  my  naked  eye. 

From  several  good  observations,  and  especially  from  one 
on  a  cinclis,  widely  opened,  that  happened  to  be  close  to 
the  edge  of  the  parapet  of  a  dianthus,  I  perceived  that  the 
passage  is  not  absolutely  open,  at  least  in  ordinary ;  but 
that  an  exceedingly  thin  film  lies  across  it.  By  delicate 
focussing,  I  have  detected  repeatedly,  in  different  degrees 
of  expansion,  and  even  at  the  widest,  the  granulations  of  a 
membrane  of  extreme  tenuity,  and  one  or  two  scattered 
cnidcB,  across  the  bright  interval.  On  another  occasion,  in 
the  case  of  a  cinclis  at  the  edge  of  the  parapet,  a  position 
singularly  favourable  for  observation,  I  saw  that  this  subtle 
film  was  gradually  pushed  out  until  it  assumed  the  form  of 


SEA-ANEMONES:  THEIR  WEAPONS.  861 

a  hemispherical  bladder,  in  which  state  it  remained  as  long 
as  I  looked  at  it.  At  the  same  time  the  outline  of  the 
cinclis  itself  was  sharp  and  clear,  when  brought  into  focus 
further  in.  The  film,  whatever  it  be,  is  superficial,  and 
does  not  appear  to  be  a  portion  of  the  integument  proper. 
I  take  it  to  be  a  film  of  mucus  (composed  of  deorganised 
epithelial  cells),  which  is  constantly  in  process  of  being 
sloughed  from  all  the  superficial  tissues  in  this  tribe  of 
animals,  and  which  continues  tenaciously  to  invest  their 
bodies,  until,  corrugated  by  the  successive  contractions  of 
the  animal,  it  is  washed  away  by  the  motions  of  the  waves. 
As,  however,  one  film  is  no  sooner  removed  than  another 
begins  to  form,  one  would  always  expect  external  pores 
so  minute  as  these  to  be  veiled  by  a  mucus-film  in  seasons 
of  rest. 

The  pressure  of  this  film  is  sufficient  evidence  that 
the  cinclides  are  not  excretory  orifices  for  the  outflow  of 
the  respired  water  in  the  manner  of  the  discharging  siphon 
in  the  Bivalve  MOLLUSCA  : — at  least  that  no  current  con- 
stantly, or  even  ordinarily,  passes  through  them.  I  have 
watched  them  continuously  for  periods  sufficient  to  detect 
such  discharge  if  it  were  periodic.  On  one  occasion  (viz., 
that  in  which  the  film  was  protruded  like  a  blown  bladder) 
a  minute  Infusorial  animalcule  chanced  to  pass  across, 
close  to  the  surface  of  the  film  :  this  would  have  been  a 
decisive  test  of  the  existence  of  a  ciliary  current ;  but  not 
the  slightest  deviation  in  the  little  atom's  course  could  be 
detected. 

That  the  cinclides  are  the  special  orifices  through  which 
those  missile  weapons,  the  acontia,  are  shot  and  re- 
covered, rests  not  merely  on  the  probability  that  arises 
from  the  co-existence  of  the  two  series  of  facts  I  have 
above  recorded,  but  upon  actual  observation.  In  a  rather 
large  S.  dianthiis,  somewhat  distended,  placed  in  a  glass 
vessel  between  my  eye  and  the  sun,  I  saw,  with  great 
distinctness,  by  the  aid  of  a  pocket-lens,  many  acontia 


862  EVENINGS   AT    THE  MICROSCOPE. 

protruded  from  the  cinclides,  and  many  more  of  the  latter 
widely  open.  The  ancontia,  in  some  cases,  did  not  so  ac- 
curately fill  the  orifice  but  that  a  line  of  bright  light  (or 
of  darkness,  according  as  the  sun  was  exactly  opposite 
or  not)  was  seen  partially  bordering  the  issue  of  the 
thread,  while  the  thickened  rim  of  the  cinclis  surrounded 
all. 

The  appearance  of  the  orifices  whence  the  acontia 
issued  was  that  of  a  tubercle  or  wart,  and  the  same  ap- 
pearance I  have  repeatedly  marked  in  examples  observed 
on  the  stage  of  the  microscope  ;  namely,  that  of  a  per- 
forate pimple,  or  short  columnar  tube.  This  was  clearly 
manifest  when  the  animal,  slowly  swaying  to  and  fro, 
brought  the  sides  of  the  cinclis  into  partial  perspective. 

On  another  occasion  I  witnessed  the  actual  issue  of  the 
acontia  from  the  cinclides.  I  was  watching,  under  a  low 
power  of  the  microscope,  a  specimen  of  a  S.  nivea,  while, 
by  touching  its  body  rudely,  I  provoked  it  to  emit  its 
missile  filaments.  Presently  they  burst  out  with  force, 
not  all  at  once,  but  some  here  and  there,  then  more,  and 
yet  more,  on  the  repeated  contractions  of  the  corrugating 
walls  of  the  body.  Occasionally,  the  free  extremity  of  a 
filament  would  appear,  but  more  frequently  the  bight  of  a 
bent  one ;  and  very  often  I  saw  two,  and  even  three,  issue 
from  the  same  cinclis.  The  successive  contractions  of  the 
animal  under  irritation,  caused  the  acontia  already  pro- 
truded to  lengthen  with  each  fresh  impetus,  the  bights 
still  streaming  out  in  long  loops,  till  perhaps  the  free  end 
would  be  liberated,  and  it  would  be  a  loop  no  longer ;  and 
sometimes  a  new  thread  would  shoot  from  a  cinclis, 
whence  one  or  two  long  ones  were  stretching  already ; 
while,  as  often,  the  new-comers  would  force  open  new 
cinclides  for  themselves.  The  suddenness  and  explosive 
force  with  which  they  burst  out,  appeared  to  indicate  a 
resistance  which  was  at  length  overcome : — perhaps  (in 
part  at  least)  due  to  the  epithelial  film  above  mentioned, 


SEA-ANEMONES  I    THETB   WEAPONS.  863 

or  to  an  actual  epiderm,*  which,  though  often  ruptured, 
has  ever,  with  the  aptitude  to  heal  common  to  these  lowly 
structures,  the  power  of  quickly  uniting  again. 

It  appeared  to  me  manifest,  from  this  and  other  similar 
observations,  that  no  such  arrangement  exists  as  that 
which  I  had  fancied — that  a  definite  cinclis  is  assigned 
to  a  definite  acontium,  or  pair  of  acontia;  and  that  the 
extremity  of  the  latter  is  guided  to  the  former,  with  un- 
erring accuracy,  by  some  internal  mechanism,  whenever 
the  exercise  of  the  defensive  faculty  is  desired.  What  I 
judge  to  be  the  true  state  of  the  case  is  as  follows  :  The 
acontia,  fastened  by  one  end  to  the  septa,  or  the  mem- 
branes which  support  them,  lie,  while  at  rest,  irregularly 
coiled  up  along  the  narrow  interseptal  hollows.  The 
outer  walls  of  these  hollows  are  pierced  with  the  cinclides. 
When  the  animal  is  irritated,  it  immediately  contracts  : 
the  water  contained  in  the  visceral  cavity  finds  vent  at 
these  natural  orifices,  and  the  forcible  currents  carry  with 
them  the  acontia,  each  through  that  cinclis  which  happens 
to  lie  nearest  to  it.  The  frequency  with  which  a  loop  is 
forced  out  shows  that  the  issue  is  the  result  of  a  merely 
mechanical  action  ;  which  is,  however,  not  the  less  worthy 
of  admiration  because  of  the  simplicity  of  the  contrivance  ; 
nor  the  less  manifestly  the  result  of  Divine  wisdom  work- 
ing to  a  given  end  by  perfectly  adequate  means.  The 
ejected  acontia,  loaded  with  their  deadly  cnida  in  every 
part  of  their  length,  carry  abroad  their  fatal  powers  not 
the  less  surely  than  if  each  had  been  provided  with  a 
proper  tube  leading  from  its  free  extremity  to  the  nearest 
cinclis. 

Curious  as  these  contrivances  are,  there  is  yet  much 
more  to  be  told :  these  are  preparatory  and  ancillary,  as 
it  were,  to  the  elaborate  mechanism  by  which  the  ultimate 
object  of  the  whole  provision  is  to  be  attained.  The 

*  The  outer  covering  of  the  external  surface  of  the  body,  commonly 
called  the  cuticle  or  scarf-skin. 


EVENINGS    AT    THE    MICROSCOPE. 


acontium  is  but  a  reservoir  for  the  weapons, — a  kind  of 
quiver  for  the  arrows  ;  and  the  cinclis  is  a  provision  for 
getting  them  ready  for  action  :  we  have  not  yet  looked  at 
the  arrows  themselves. 

They  occur  under  three  principal  forms ;  and  for  the 
investigation  of  these  we  shall  find  it  convenient  to  have 
recourse  to  different  species. 

The  first  and  most  generally  distributed  form  is  the 
Chambered  Cnida,  as  it  is  also  the  most  elaborately 
organised.  I  know  of  no  species  in  which  it  can  be  exa- 
mined under  so  favourable  circumstances  as  the  pretty 
Madrepore  (Caryophyllia  Smithii)  of  our  south-western 
coasts  ;  and,  as  I  have  several  specimens 
of  that  species  in  my  aquarium,  subjects  are 
at  hand  for  our  investigation.  The  clear  ten- 
tacles are,  as  you  perceive,  crowned  with 
opaque  globular  heads  ;  if  I  should  nip  off 
one  of  these  heads,  and  flatten  it  by  means 
of  the  compressorium,  you  would  see  it 
literally  composed  of  cnida,  the  ends  of 
which  project  side  by  side,  as  close  as 
they  can  be  packed  one  against  another. 

But  still  larger  examples  may  be  ob- 
tained from  the  craspeda.  With  a  smart, 
sudden  blow  I  break  the  stony  skeleton  of 
the  Madrepore  in  sunder — the  flesh  tear- 
ing apart  also ;  and  thus  I  expose  the 
interior  of  the  living  animal.  A  great 
number  of  pellucid  ribbons  are  now  seen, 
very  much  convoluted,  which  are  named 
craspeda.  These  are  almost  composed  of 
large  cnida. 

I  remove  with  fine  pliers  a  small  frag- 
ment of  one  of  these  ribbons,  and  placing 
it  between  the  plates  of  the  compressorium, 
flatten  it  gradually  till  the  plates  are  brought 


SEA-ANEMONES  I    THEIR    WEAPONS.  865 

into  as  close  contact  as  they  can  be.  A  high  power  now 
being  put  on,  examine  the  organs  in  question. 

You  see  a  multitude  of  perfectly  transparent,  colourless 
vesicles,  of  a  lengthened  ovate  figure,  considerably  larger 
at  one  end  than  at  the  other ;  one  of  average  dimensions 
measures  in  length  ^ru^  of  an  inch,  and  in  greatest 
diameter  -s-gV^th.  In  the  larger  (the  anterior)  moiety, 
passing  longitudinally  through  its  centre,  is  seen  a  slender 
chamber,  fusiform  or  lozenge-form,  about  ^sV^th  of  an 
inch  in  its  greatest  transverse  diameter,  and  tapering  to  a 
point  at  each  extremity.  The  anterior  point  merges  into 
the  walls  of  the  cnida  at  its  extremity ;  while  the  posterior 
end,  after  having  become  attenuated  like  the  anterior, 
dilates  with  a  funnel-shaped  mouth,  in  which  the  eye  can 
clearly  see  a  double  infolding  of  the  chamber-wall.  After 
this  double  fold  the  structure  proceeds  as  a  very  slender 
cord,  which,  passing  back  towards  the  anterior  end  of  the 
capsule,  winds  loosely  round  and  round  the  chamber,  with 
some  regularity  at  first,  but  becoming  involved  in  contor- 
tions more  and  more  intricate,  as  it  fills  up  the  posterior 
moiety  of  the  cavity.  The  fusiform  chamber  appears  to 
be  marked  on  its  inner  surface  with  regularly  recurring 
serrations,  which  are  the  optical  expression  of  that  peculiar 
armour  to  be  described  presently. 

Under  the  stimulus  of  pressure,  when  subjected,  as 
now,  to  microscopical  examination,  and  doubtless  under 
nervous  stimulus,  subject  to  the  control  of  the  will,  during 
the  natural  exercise  of  the  animal's  functions, — the  cnida 
suddenly  emit  their  contents  with  great  force,  in  a  regular 
and  prescribed  manner.  It  must  not  be  supposed,  how- 
ever, that  the  pressure  spoken  of  is  the  immediate  mechani- 
cal cause  of  the  emission :  the  contact  of  the  glass-plates 
of  the  compressorium  is  never  so  absolute  as  to  exert  the 
least  direct  force  upon  the  walls  of  the  capsule  itself;  but 
the  disturbance  produced  by  the  compression  of  the  sur- 
rounding tissues  excites  an  irritability,  which  evidently  re- 


366  EVENINGS    AT    THE    MICKOSCOPE. 

sides  in  a  very  high  degree  in  the  interior  of  the  cnida ; 
and  the  projection  of  the  contents  is  the  result  of  a  vital 
force. 

In  general,  the  eye  can  scarcely,  or  not  at  all,  follow 
the  lightning-like  rapidity  with  which  the  chamber  and  its 
twining  thread  are  shot  forth  from  the  larger  end  of  the 
cnida.  But  sometimes  impediments  delay  the  emission, 
or  allow  it  to  proceed  only  in  a  fitful  manner,  a  minute 
portion  at  a  time ;  and  sometimes,  from  the  resistance  of 
friction  (as  against  the  glass  plate  of  the  compressorium), 
the  elongation  of  the  thread  proceeds  evenly,  but  so  slowly 
as  to  be  watched  with  the  utmost  ease  ;  and  sometimes  the 
process  which  has  reached  a  certain  point  normally,  be- 
comes from  some  cause  arrested,  and  the  contents  of  the 
cell  remain  permanently  fixed  in  a  transition  state.  Thus, 
a  long  continued  course  of  patient  observation  is  pretty 
sure  to  present  some  fortuitous  combinations,  and  abnor- 
mal conditions,  which  greatly  elucidate  phenomena,  that 
normally  seemed  to  defy  investigation. 

In  watching  any  particular  cnida,  the  moment  of  its 
emission  may  be  predicted  with  tolerable  accuracy,  by  the 
protrusion  of  a  nipple -shaped  wart  from  the  anterior  ex- 
tremity. This  is  the  base  of  the  thread.  The  process  of 
its  protrusion  is  often  slow  and  gradual,  until  it  has 
attained  a  length  about  equal  to  twice  its  own  diameter, 
when  it  suddenly  yields,  and  the  contents  of  the  cnida  dart 
forth.  At  this  instant  I  have,  in  many  instances,  heard  a 
distinct  crack  or  crepitation,  both  in  the  examination  of 
this  species  and  of  Sagartia  parasitica. 

When  fully  expelled,  the  thread  or  wire,  which  is 
distinguished  by  the  term  ecthoreum,  is  often  twenty, 
thirty,  or  even  forty  times  the  length  of  the  cnida; 
though  in  some  species,  as  in  most  of  the  Sagartia,  it 
frequently  will  not  exceed  one-and-a-half  or  two  times  the 
length  of  the  cnida. 

The  ecthorea  which  are  discharged  by  chambered  cnidce, 


SEA- ANEMONES  !  THEIR  WEAPONS. 


867 


are  invariably  furnished  with  a  peculiar  armour.  The 
basal  portion,  for  a  length  equal  to  that  of  the  cnida,  or 
a  little  more,  is  distinctly  swollen,  but  at  the  point  indi- 
cated it  becomes  (often  abruptly)  at- 
tenuated, and  runs  on  for  the  remainder 
of  its  length  as  an  excessively  slender 
wire  of  equal  diameter  throughout.  In 
the  short  ecthorea  of  Sagartia  the  atte- 
nuated portion  is  obsolete. 

It  is  chiefly  upon  this  ventricose  or 
swollen  basal  portion  that  the  elaborate 
armour  is  seen,  which  is  so  characteristic 
of  these  remarkable  organs.  For  around 
its  exterior  wind  one  or  more  spiral 
thickened  bands,  varying  in  different 
species  as  to  their  number,  the  number 
of  volutions  made  by  each,  and  the 
angle  which  the  spiral  forms  with  the 
axis  of  the  ecthoreum.  The  whole  spiral 
formed  of  these  thickened  bands  is 
termed  the  screw,  or  strebla. 

In  the  ecthorea  emitted  by  chambered 
cnida  from  the  craspeda  of  Tealia  eras- 
sicornis,  the  screw  is  formed  of  a  single 
band,  having  an  inclination  of  45°  to  the 
axis,  and  becoming  invisible  when  it  has 
made  seven  volutions.  In  those  from 
the  same  organ  in  S.  parasitica,  we  find 
the  screw  of  two  equidistant  bands, 
each  of  which  makes  about  six  turns — 
twelve  in  all — having  an  inclination  of  70°  from  the  com- 
mon axis.  In  those  similarly  placed  in  Caryophyllia 
Smithii  [now  under  your  observation],  the  strebla  is  com- 
posed, as  you  may  perceive,  of  three  equidistant  bands, 
each  of  which  makes  about  ten  turns — thirty  in  all — 
with  an  inclination  of  about  40°  from  the  axis.  In  every 


CXIDA    OP 
TKAUA  CRA88ICORJJI8. 

(discharged). 


368  EVENINGS    AT  THE    MICROSCOPE. 

case  the  spiral  runs  from  the  east  towards  the  north,  sup- 
posing the  axis  to  point  perpendicularly  upwards. 

Sometimes,  especially  after  having  been  expelled  for 
some  time,  the  wall  of  the  ecthoreum  becomes  so  attenuated 
as  to  be  evanescent,  while  the  strebla  is  still  distinctly 
visible.  An  inexperienced  observer  would  be  liable,  under 
such  circumstances,  to  suppose  that  the  screw,  when 
formed  of  a  single  band,  as  in  T.  crassicornis,  is  itself  the 
wire ;  an  error  into  which  I  had  myself  formerly  fallen. 
An  error  of  another  kind  I  fell  into,  in  supposing  that 
the  triple  screw  of  the  wire  in  (7,  Smithii  was  a  series  of 
overlapping  plates  :  the  structure  of  the  weapon  is  the 
same  in  all  cases  (with  the  variations  in  detail  that  I  have 
just  indicated) ;  and  the  structure  is,  I  am  now  well  as- 
sured, a  spiral  thickened  band  running  round  the  wall  of 
the  ecthoreum  on  its  exterior  .  surface.  I  have  been  able, 
when  examining  such  large  forms  as  these  of  Corynactis 
viridis  and  Caryophyllia  Smithii,  with  a  power  of  750 
diameters,  to  follow  the  course  of  the  screw,  as  it  alter- 
nately approached  and  receded  from  the  eye,  by  altering 
the  focus  of  the  object-glass,  so  as  to  bring  each  part  suc- 
cessively into  the  sphere  of  vision. 

These  thickened  spiral  bands  afford  an  insertion  for  a 
series  of  firm  bristles,  which  appear  to  have  a  broad  base 
and  to  taper  to  a  point.  Their  length  I  cannot  determi- 
nately  indicate,  but  I  have  traced  it  to  an  extent  which 
considerably  exceeds  the  diameter  of  the  ecthoreum. 
These  barbed  bristles  are  denominated  pterygia. 

The  number  of  pterygia  appears  to  vary  within  slight 
limits.  As  well  as  I  have  been  able  to  make  out,  there 
are  but  eight  in  a  single  volution  of  the  one-banded  strebla 
in  T.  crassicornis ;  while  in  the  more  complex  screws  of 
8.  parasitica,  Cor.  viridis,  and  Car.  Smithii,  there  appear 
to  be  twelve  in  each  volution. 

The  barbs,  when  they  first  appear,  invariably  project  in 
a  diagonal  direction  from  the  ecthoreum ;  and  sometimes 


SEA- ANEMONES  :    THEIR   WEAPONS.  869 

they  maintain  this  posture.  But  more  commonly,  either 
in  an  instant,  or  slowly  and  gradually,  they  assume  a 
reverted  direction. 

From  some  delicate  observations  made  with  a  very 
good  light,  I  have  reason  to  conclude  that  the  strebla,  and 
even  the  pterygia,  are  continued  on  the  attenuated  portion 
of  the  ecthoreum,  perhaps  throughout  its  length.  In  Cor. 
viridis  and  Car.  Smithii,  I  have  succeeded  in  tracing  them 
up  a  considerable  distance.  In  the  latter  I  saw  the  con- 
tinuation of  all  these  bands  with  their  bristles ;  but,  what 
was  strange,  the  angle  of  inclination  had  become  nearly 
twice  as  acute  as  before,  being  only  22°  from  the  axis. 
The  appearance  of  the  attenuate  portion,  as  also  of  the 
base  of  the  ventricose  part,  is  exactly  that  of  a  three- sided 
wire,  twisted  on  itself;  the  barbs  projecting  from  the 
angles. 

The  next  form  of  these  organs  is  the  Tangled  Cnida. 
This  form  is  very  generally  distributed,  and  is  mingled 
with  the  former  in  the  various  tissues.  In  the  genus 
Sagartia,  however,  it  is  by  far  the  rarer  form,  while  in 
Actinia  and  Anihea  it  seems  to  be  the  only  one. 

The  pretty  little  Corynactis  viridis  is  the  best  species 
that  I  am  acquainted  with  for  studying  this  kind  of  cnidce. 
A  fragment  of  its  craspeda  I  have  here  ready  for  your 
observation,  prepared  exactly  like  that  of  C.  Smithii.  The 
figure  of  the  cnida  is  nearly  that  of  a  perfect  oval,  but  a 
little  flattened  in  one  aspect,  about  ^^th  °^  an  "1C^1  'lu  ^ne 
longer,  and  T^th  in  the  shorter  diameter.  Their  size, 
therefore,  makes  them  peculiarly  suitable  for  observations 
on  the  structure  and  functions  of  these  curious  organs. 
Within  the  cavity  lies  a  thread  (ecthoreum)  of  great  length 
and  tenuity,  coiled  up  in  some  instances  with  an  approach 
to  regularity,  but  much  more  commonly  in  loose  contor- 
tions, like  an  end  of  thread  rudely  rolled  into  a  bundle 
with  the  fingers. 

The  armour  of  this  kind  does  not  differ  essentially 
B  B 


370 


EVENINGS    AT    THE    MICROSCOPE. 


from  that  already  described.  It  is  true  I  have  detected  it 
only  in  Corynactis,  where  the  short  ecthoreum  of  the 
Tangled  Cnida  is  surrounded  throughout  its  length  by  a 
barbed  strebla  of  three  bands.  The  barbs  are  visible, 
under  very  favourable  conditions  for  observation,  even 
while  the  tangled  wire  remains  inclosed  in  the  cnida,  but 
their  optical  expression  is  that  of  serratures  of  the  walls, 
without  the  least  appearance  of  a  screw.  This,  I  say,  is 
the  only  species  in  which  I  have  actually  seen  the  arma- 
ture of  the  ecthoreum  in  this  kind  of  cnida,  but  I  infer  its 
existence  from  analogy  in  other 
species,  where  the  conditions  that 
can  be  recognised  agree  with  those 
in  this,  though  the  excessive  attenu- 
ation of  the  parts  precludes  actual 
observation  of  the  structure  in  ques- 
tion. 

Spiral  Cnidae  constitute  the  third 
form.  In  a  few  species,  as  Sagartia 
parasitica,  Tealia  crassicornis,  and  Ce- 
rianthus  membranaceus,  I  have  found 
very  elongated  fusiform  cnidce,  which 
seem  composed  of  a  slender  cylin- 
drical thread,  coiled  into  a  very  close 
and  regular  spiral.  In  some  .cases 
the  extremities  are  obtuse,  but  in 
others,  as  in  T.  crassicornis,  an  ex- 
ample of  which  I  now  show  you, 
the  posterior  extremity  runs  off  to  a 
finely-attenuated  point,  the  whole  of  the  spire  visible  even 
to  the  last,  the  whole  bearing  no  small  resemblance  to  a 
multispiral  shell ;  as  one  of  the  Cerithiadce  or  Turritelladce. 
The  ecthoreum  is  discharged  reluctantly  from  this  form, 
and  I  have  never  seen  an  example  in  which  the  whole  had 
been  run  off.  So  exceedingly  subtle  are  the  walls  of  the 
cnida,  that  it  was  not  until  after  many  observations  that 


CNIDA   OF   CORYNACTIS. 


SEA- ANEMONES  :  THEIB  WEAPONS.         871 

I  detected  them ;  in  an  example  from  T.  crassicornis, 
which  had  discharged  about  half  of  the  wire,  I  have  not 
seen  the  slightest  sign  of  armature  on  the  ecthoreum.  So 
far  as  my  investigations  go,  these  Spiral  Cnidae  are  con- 
fined to  the  walls  of  the  tentacles,  in  which,  however,  they 
are  the  dominant  form.* 

Such,  then,  are  the  form  and  armour  of  these  organs. 
But  I  have  not  yet  done  with  them.  The  emission  of  the 
wire,  strange  to  say,  is  a  process  of  distinct  evolution,  or 
expansion  from  within,  from  beginning  to  end.  The  ectho- 
reum is  not  a  solid,  but  a  tubular,  prolongation  of  the 
walls  of  the  cnida,  turned-in,  in  its  first  condition,  like 
the  finger  of  a  glove  drawn  inwards.  Of  this  fact  you 
may  convince  yourself  by  a  careful  watching  of  the  phe- 
nomena before  you.  Many  of  the  ecthorea  from  the  tangled 
cnida  now  under  your  eye  run  out,  not  in  a  direct  line, 
but  in  a  spiral  direction.  Select  one  of  these,  and  you 
will  perceive  that  each  bend  of  the  spire  is  made,  and 
stereotyped,  so  to  speak,  in  succession,  while  the  tips  go 
on  lengthening ;  the  tip  alone  progresses,  the  whole  of  the 
portion  actually  discharged  remaining  perfectly  fixed ; 
which  could  not  be  on  any  other  supposition  than  that  of 
evolution. 

In  the  discharge  of  the  chambered  kind — to  revert  to 
those  which  we  were  just  now  examining — we  saw  the 
ventricose  basal  part  first  appear;  the  lower  barbs  flew 
out  before  the  upper  ones,  and  all  were  fully  expanded 
before  the  attenuated  portion  began  to  lengthen.  This, 
again,  is  consistent  only  with  the  fact  of  the  evolution  of 
the  whole.  On  several  occasions  of  observation  on  the 
chambered  cnida  of  C.  Smithii,  I  have  actually  seen  the 
unevolved  portion  of  the  ecthoreum  running  out  through 
the  centre  of  the  evolved  ventricose  portion.  But  per- 
haps the  most  instructive  and  convincing  example  of  all 

*  These  details,  with  many  others,  are  given  in  my  Hist,  of  Brit. 
Sea-anemones  and  Corals,  Introd.,  xxii— xl. 
B   B   2 


372  EVENINGS   AT    THE   MICBOSCOPE. 

was  the  following.  One  of  the  large  tangled  cnid®  of 
Corynactis  viridis  had  shot  about  half  of  its  wire  with 
rapidity,  when  a  kind  of  twist,  or  "  kink,"  occurred  against 
the  nipple  of  the  cnida,  whereby  the  process  was  sud- 
denly arrested.  The  projectile  force,  however,  continuing, 
caused  the  impediment  to  yield,  and  minute  portions  of 
the  thread  flew  out  piecemeal,  by  fits  and  starts.  By 
turning  the  stage- screw,  I  brought  the  extremity  of  the 
discharged  portion  into  view,  and  saw  it  slowly  evolving, 
a  little  at  a  time.  Turning  back  to  the  cnida,  I  saw  the 
kink  gradually  give  way,  and  the  whole  of  the  tangled 
wire  quickly  flew  out  through  the  nipple.  I  once  more 
moved  the  stage,  following  up  the  ecthoreum,  and  pre- 
sently found  the  true  extremity,  and  a  large  portion  of 
the  wire  still  inverted ;  slowly  evolving,  indeed,  but  very 
distinct  throughout  its  whole  course,  within  the  walls  of 
the  evolved  portion. 

From  all  these  observations  there  cannot  remain  a  doubt 
of  the  successive  evolution  of  the  entire  ecthoreum. 

You  ask,  What  is  the  nature  of  the  force  by  which  the 
contained  thread  is  expelled  ?  That  it  is  a  potent  force  is 
obvious  to  any  one  who  marks  the  sudden  explosive 
violence  with  which  the  nipple-like  end  of  the  cnida 
gives  way,  and  the  contents  burst  forth ;  as  also  the  ex- 
treme rapidity  with  which,  ordinarily,  the  whole  length  is 
evolved.  A  curious  example  of  this  force  once  excited 
my  admiration.  The  ecthoreum  from  a  cnida  of  Corynactis 
viridis  was  in  course  of  rapid  evolution,  when  the  tip 
came  full  against  the  side  of  another  cnida  already 
emptied.  The  evolution  was  momentarily  arrested,  but 
the  wall  of  the  empty  capsule  presently  was  seen  to  bend 
inward  and  suddenly  to  give  way,  the  ecthoreum  forcing 
itself  in,  and  shooting  round  and  round  the  interior  of  the 
cnida. 

The  most  careful  observations  have  failed  to  reveal  a 
lining  membrane  to.  the  cnida.  I  have  repeatedly  dis- 


SEA- ANEMONES  :  THEIB  WEAPONS.         878 

cerned  a  double  outline  to  the  walls  themselves,  the  op- 
tical expression  of  their  diameter;  but  have  never  de- 
tected any,  even  the  least,  appearance  of  any  tissue  start- 
ing from  the  walls,  as  the  ecthoreum  bursts  out.  My  first 
supposition,  reluctantly  resigned,  was,  that  some  such 
lining  membrane,  of  high  contractile  power,  lessened,  on 
irritation,  the  volume  of  the  cavity,  and  forced  out  the 
wire. 

The  cnida  is  filled,  however,  with  a  fluid.  This  is 
very  distinctly  seen  occupying  the  cavity,  when,  from  any 
impediment,  such  as  above  described,  the  wire  flies  out 
fitfully ;  waves,  and  similar  motions,  passing  from  wall  to 
wall.  Sometimes,  even  before  any  portion  of  the  wire 
has  escaped,  the  whole  mass  of  tangled  coils  is  seen  to 
move  irregularly  from  side  to  side,  within  the  capsule, 
from  the  operation  of  some  intestine  cause.  The  emission 
itself  is  a  process  of  injection ;  for  I  have  many  times  seen 
floating  atoms  driven  forcibly  along  the  interior  of  the 
ecthoreum,  sometimes  swiftly,  and  sometimes  more  delibe- 
rately. Nothing  that  I  have  seen  would  lead  me  to  con- 
clude that  the  wall  of  the  cnida  is  ciliated. 

I  consider,  then,  that  this  fluid,  holding  organic 
corpuscles  in  suspension,  is  endowed  with  a  high  degree 
of  expansibility ;  that,  in  the  state  of  repose,  it  is  in  a 
condition  of  compression,  by  the  inversion  of  the  ectho- 
reum ;  and  that,  on  the  excitement  of  a  suitable  stimulus, 
it  forcibly  exerts  its  expansile  power,  distending,  and,  con- 
sequently, projecting,  the  tubular  ecthoreum, — the  only 
part  of  the  wall  that  will  yield  without  actual  rupture. 

It  has  been  proved  that  the  execution  of  these  weapons 
is  as  effectual  as  their  mechanism  is  elaborate.  The  wire 
shot  with  such  force  penetrates  even  to  its  base  the  tissues 
of  the  living  animals  which  the  Anemone  attacks ;  and  then 
its  barbs  preclude  the  withdrawal  of  the  dart.  But  the  en- 
trance of  bodies  so  excessively  slender  would  of  itself 
inflict  little  injury ;  there  is  evidently  the  infusion  at  the 


374  EVENINGS    AT    THE    MICROSCOPE. 

same  time  of  a  highly  subtle  poison  into  the  wound ;  some 
venomous  fluid  escaping  with  the  discharge  of  the  ectho- 
reum,  which  has  the  power,  at  least  when  augmented  by 
the  simultaneous  insertion  of  scores,  or  hundreds,  of  the 
weapons,  of  suddenly  arresting  animal  vigour  and  speedily 
destroying  life,  even  in  creatures — fishes,  for  example — 
far  higher  than  the  Zoophyte  in  the  scale  of  organisation. 
I  have  seen  a  little  fish  in  perfect  health  come  into  acci- 
dental contact  with  one  of  the  acontia  of  an  irritated 
Sagartia,  when  all  the  evidences  of  distress  and  agony 
were  instantly  manifested ;  the  little  creature  darted  wildly 
to  and  fro,  turned  over,  sank  upon  the  bottom,  struggled, 
flurried,  and  was  dead. 

Admitting  the  existence  of  a  venomous  fluid,  it  is  dif- 
ficult to  imagine  where  it  is  lodged  and  how  it  is  injected. 
The  first  thought  that  occurs  to  one's  mind  is,  that  it  is 
the  organic  fluid  which  we  have  seen  to  fill  the  cnida,  and 
to  be  forced  through  the  everting  tubular  ecthoreum.  But 
if  so,  it  cannot  be  ejected  through  the  extremity  of  the 
ecthoreum,  because  if  this  were  an  open  tube,  I  do  not  see 
how  the  contraction  of  the  fluid  in  the  cnida  could  force  it 
to  evolve  ;  the  fluid  would  escape  through  the  still  inverted 
tube.  It  is  just  possible  that  the  barbs  may  be  tubes  open 
at  the  tips,  and  that  the  poison-fluid  may  be  ejected 
through  these.  But  I  rather  incline  to  the  hypothesis, 
that  the  cavity  of  the  ecthoreum,  in  it*  primal  inverted  con- 
dition, while  it  yet  remains  coiled  up  in  the  cnida,  is 
occupied  with  the  potent  fluid  in  question,  and  that  it  is 
poured  out  gradually  within  the  tissues  of  the  victim,  as 
the  evolving  tip  of  the  wire  penetrates  farther  and  farther 
into  the  wound. 

I  do  not  think  that  the  whole  range  of  organic  exist- 
ence affords  a  more  wonderful  example  than  this  of  the 
minute  workmanship  and  elaboration  of  the  parts;  the 
extraordinary  modes  in  which  certain  prescribed  ends  are 
attained,  and  the  perfect  adaptation  of  the  contrivance  to 


SEA-ANEMONES:  THEIB  WEAPONS.  375 

the  work  which  it  has  to  do.  We  must  remember  that  all 
this  complexity  is  found  in  an  animal  which  it  is  customary 
to  consider  as  of  a  very  simple  structure.  But  the  ways 
of  God  are  past  finding  out.  These  are  but  parts  of  His 
ways.* 

*  The  presence  of  these  very  remarkable  organs  is  not  limited  to  the 
Actinoids.  They  exist  in  the  entire  class  of  Polyps,  including  the 
Medusae,  also  in  the  Synaptce  (see  p.  299  supra),  many  Turbellarice,  some 
of  the  Annelids,  and  a  few  among  the  Mollusca.  Dr.  R.  Bergh  of 
Copenhagen  has  published  (1861)  some  elaborate  researches,  proving 
the  existence  of  urticating  cnidae,  in  abundance,  in  several  forms  of  the 
charming  Naked-gilled  Mollusca,  allied  to  Eolis ;  while  they  seem  to  be 
wanting  in  the  tougher-skinned  Doris,  <fcc, 


376  EVENINGS   AT    THE    MICROSCOPE. 


CHAPTER  XX. 

PEOTOZOA  AND   SPONGES. 

WE  are  so  accustomed  to  see  certain  of  the  vital  functions 
of  animals  performed  by  special  organs  or  tissues,  that  we 
wonder  when  we  find  creatures  which  move  without  limbs, 
contract  without  muscles,  respire  without  lungs  or  gills, 
and  digest  without  a  stomach  or  intestines.  But  thus  we 
are  taught  that  the  function  is  independent  of  the  organ, 
and,  as  it  were,  prior  to  it ;  though  in  nine  hundred  and 
ninety-nine  cases  out  of  a  thousand  it  be  associated  with 
it.  In  truth,  the  simplest  forms  of  animal  life  display 
very  little  of  that  division  of  labour,  the  minuteness  of 
which  increases  as  we  ascend  the  organic  scale ;  the 
common  tissue  is  not  yet  differentiated*  (to  use  the 
awkward  term  which  is  becoming  fashionable  among  physi- 
ologists) into  organs,  but  it  is  endowed  with  the  power 
of  fulfilling  various  offices,  and  performing  many  functions. 
In  all  probability,  the  function  is  but  imperfectly  performed; 
the  specialisation  of  certain  tissues,  and  their  union  into 
organs,  and  the  complexity  of  such  combinations,  no 
doubt,  perform  the  given  function  in  a  far  more  complete 
degree ;  and  it  is  the  number  and  elaborateness  of  these 
that  constitute  one  animal  higher  in  the  scale  than 
another.  The  human  lung  is  no  doubt  a  more  complete 
breathing  apparatus  than  the  entire  ciliated  surface  of  an 
Infusory,f  and  the  human  eye  sees  more  perfectly  than 

*  The  term  is  used  to  express  the  cellular  development  of  an  organi- 
sation from  its  original  germ. 

t  The  name  given  to  a  class  of  minute  animals,  from  their  being 
generally  developed  in  infusions  of  animal  or  vegetable  matter. 


PROTOZOA  AND  SPONGES.  877 

the  loose  aggregation  of  pigment  granules  on  the  edge  of 
a  Medusa.  But  this  diversity  is  essential  to  creation,  as 
the  great  and  wondrous  plan  which  we  see  it  to  be ;  and, 
meanwhile,  we  may  rest  satisfied  that  the  humble  require- 
ments of  the  lowest  organism  are  met  adequately  by  its 
humble  endowments. 

This  evening  I  propose  to  show  you  some  of  these  humble 
conditions  of  animal  life — the  lowest  of  the  lowly.  I  have 
here  two  or  three  phials  of  very  rich  water  which  have  been 
dipped  into  the  fresh-water  ponds  in  the  neighbourhood. 
All  collections  of  water  are  not  equally  productive ;  and 
very  far  indeed  is  the  popular  notion  from  correctness,  that 
every  drop  of  water  which  we  drink  contains  millions  of 
animalcules.  You  may  find  many  collections  of  clear 
water,  springs,  streams,  and  pools,  from  which  you  may 
examine  drop  after  drop  in  succession,  with  the  highest 
powers  of  the  microscope,  and  scarcely  discover  a  solitary 
animalcule.  Again,  it  is  not  stagnant  and  fetid  pools  that 
are  the  richest  in  vitality;  though  no  doubt  you  will 
always  obtain  some  forms  abundantly  enough  in  such 
conditions.  According  to  my  own  experience — an  expe- 
rience of  many  years — the  paucity  or  profusion  of 
animal  life  in  any  given  collection  of  water  can  never 
be  determined  beforehand ;  the  season,  the  situation, 
the  aspect,  the  character  of  the  country,  and  many 
other  unsuspected  conditions,  influence  the  result,  which 
yet  one  may  often  give  a  shrewd  guess  at.  Gener- 
ally speaking,  small  ponds,  in  which  there  is  a  good 
deal  of  vegetation  below  the  surface — and  particularly  if 
this  be  of  a  minutely-divided  character,  such  as  Myrio- 
phyUum,  Chara,  &c. — and  whose  surface  is  well  covered 
with  duckweed  (Lemna),  yield  well ;  and,  in  collecting,  it 
is  desirable  so  to  dip  as  that  some  of  the  fine  loose  sedi- 
ment of  the  bottom  may  flow  into  your  phial,  and  then  to 
pluck  up  one  or  more  of  the  filamentous  water-plants,  and 
introduce  these  into  your  vessel. 


878  EVENINGS   AT    THE    MICEOSCOPE. 

Now  to  examine  such  a  collection,  proceed  as  I  am  about 
to  show  you.  Hastily  glancing  with  the  pocket-lens  over 
the  foliage,  and  selecting  such  filaments  as  seem  the  most 
loaded  with  dirty  floccose  matter,  I  pluck  off  with  pliers 
one  or  two,  together  with  one  or  two  of  the  cleaner  ones 
that  are  higher  up  on  the  plant,  nearer  the  growing  point. 
Having  laid  these  on  the  lower  glass  of  the  live-box,  I 
take  up  with  the  tip  of  a  fine  tube,  or  a  pipette,  a  minute 
quantity  of  the  water  at  the  bottom,  which  flows  in  as  you 
see,  carrying  a  few  granules  of  the  sediment.  This  drop  I 
discharge  upon  the  glass  of  the  live-box,  put  on  the  cover, 
and  place  the  whole  on  the  stage  of  the  microscope. 

First,  let  us  use  a  low  power,  one  hundred  diameters 
or  so,  in  order  to  take  a  general  glance  at  what  we  have 
got.  Here  is  an  array  of  life,  indeed !  Motion  arrests 
the  eye  everywhere.  "  The  glittering  swift  and  the  flabby 
slow  "  are  alike  here ;  clear  crystal  globules  revolve  giddily 
on  their  axes;  tiny  points  leap  hither  and  thither  like 
nimble  fleas ;  long  forms  are  twisting  to  and  fro  ;  busy 
little  creatures  are  regularly  quartering  the  hunting-ground, 
grubbing  with  an  earnest  devotedness  among  the  sediment, 
as  they  march  up  the  stems  ;  here  are  vases  with  translucent 
bodies  protruding  from  the  mouths ;  here  are  beauteous 
bells,  set  at  the  end  of  tall  threads,  ever  lengthening  and 
shortening ;  here  are  maelstroms  in  miniature,  and  tem- 
pests in  far  less  than  a  teapot ;  rival  and  conflicting 
currents  are  whirling  round  and  round,  and  making  a 
series  of  concentric  circles  among  the  granules.  Surely 
here  is  material  for  our  study. 

I  see  an  object  slowly  creeping  along  the  glass,  which 
will  be  just  the  thing  for  our  purpose.  It  is  the  Proteus 
(Amoeba  diffluens).*  Let  me  put  on  a  higher  power,  and 
submit  it  to  your  observation. 

*  The  names  given  to  this  little  creature  are  expressive  of  its  charac- 
ter. Amoeba  is  from  the  Greek  o/u.oi/3i)  (amoibe),  signifying  change ;  and 
Proteus  in  mythology  was  an  old  prophet  of  the  sea,  who  when  seized 
assumed  all  manner  of  forms  to  avoid  uttering  his  predictions. 


PROTOZOA  AND  SPONGES.  879 

You  see  a  flat  area  of  clear  jelly,  of  very  irregular  form, 
with  sinuosities  and  jutting  points,  like  the  outline  of  some 
island  in  a  map.  A  great  number  of  minute  blackish 
granules  and  vesicles  occupy  the  central  part,  but  the 
edges  are  clear  and  colourless.  A  large  bladder  is  seen 
near  one  side,  which  appears  filled  with  a  subtle  fluid. 

But  while  you  gaze  on  it,  you  perceive  that  its  form  is 
changing :  that  it  is  not  at  two  successive  moments  of 
exactly  the  same  shape.  This  individual,  which  when  you 
first  looked  at  it  was  not  unlike  England  in  outline,  is 
now,  though  only  a  few  minutes  have  passed,  something 
totally  different;  the  projecting  angle  that  represented 
Cornwall  is  become  rounded  and  more  perpendicular ;  the 
broken  corner  that  we  might  have  called  Kent  has  formed 
two  little  points  up  in  the  position  of  Lincolnshire  ;  the 
large  bladder,  which  was  in  the  place  of  the  Eastern 
counties,  is  moved  up  to  the  Durham  coast,  and  is,  more- 
over, greatly  diminished ;  and  other  like  changes  have 
taken  place  in  other  parts. 

Lo  !  even  while  speaking  of  these  alterations,  they  have 
been  proceeding,  so  that  another  and  a  totally  diverse  out- 


FORMS   OF   AMffiBA. 

Svccetsivtly  dratcn  from  one  individual. 

line  is  now  presented.  A  great  excavation  takes  the  place 
of  Dorset ;  Kent  is  immensely  prolonged ;  the  bladder 
has  quite  disappeared,  &c.  ;  but  it  is  impossible  to  follow 
these  changes,  which  are  ever  going  on  without  a  moment's 


380  EVENINGS   AT   THE   MICBOSCOPE. 

intermission,  and  without  the  slightest  recognisable  rule  or 
order.  The  projections  are  obliterated  or  exaggerated ; 
the  sinuosities  are  smoothed,  or  deepened  into  gulfs,  or 
protruded  into  promontories ;  firths  form  here,  capes 
there  ;  but  not  by  starts,  but  evenly,  and  with  sufficient 
rapidity  to  be  appreciable  to  the  eye  while  under  actual 
observation ;  though  the  alterations  are  more  striking  if 
you  take  your  eye  off  the  object  for  a  few  seconds,  and 
then  look  again ;  and  still  more  so  if  you  try  to  sketch 
the  outline.  Individuals  vary  greatly  in  dimensions  ;  this 
specimen  is  about  one  hundred  and  twentieth  of  an  inch 
in  long  diameter,  but  others  I  have  seen  not  more  than 
one-tenth  as  large  as  this,  and  some  twice  as  large. 

Disregarding  now  this  peculiarity  of  change  of  form, 
which  has  procured  for  it  the  name  of  the  old  sea-god  that 
was  so  difficult  to  bind,  we  will  concentrate  our  attention 
on  some  other  points  not  less  interesting.  That  great 
bladder  undergoes  changes  besides  those  gradual  altera- 
tions of  place  which  are  dependent  on  the  general  form. 
It  slowly  but  manifestly  increases  in  size  up  to  a  certain 
extent,  when  it  rather  suddenly  diminishes  to  a  point,  and 
immediately  begins  to  fill  again,  as  slowly  as  before. 
These  alternations  go  on  with  some  regularity,  and  we 
cannot  observe  them  without  becoming  convinced  that  it 
is  a  process  of  filling  and  emptying;  that  the  bladder 
gradually  fills  with  a  fluid  which  is  either  secreted  by  its 
walls  or  percolates  into  it  from  the  surrounding  tissue  ; 
which  fluid,  when  full,  the  bladder  discharges  by  a  sudden 
contraction  of  its  outline.  But  whither  the  fluid  goes  it  is 
difficult  to  determine  ;  I  have  never  been  able,  in  this  or 
in  any  other  instance  of  its  occurrence — though  this  con- 
tractile bladder  is  characteristic  of  the  extensive  classes 
Infusoria  and  Eotifera — to  see  any  issue  of  fluid  from  the 
body  at  the  moment  of  contraction,  and  therefore  conclude 
that  it  is  discharged  into  the  body,  perhaps  back  again 
into  the  tissues  from  whence  it  was  taken  up,  and  from 


PROTOZOA  AND  SPONGES.  881 

whence  it  was  about  to  be  collected  again.  Hence  it  is 
probably  the  first  obscure  rudiment  of  a  circulation  ;  the 
fluids  impregnated  with  the  products  of  digestion  being 
thus  collected  and  then  diffused  throughout  the  soft  and 
yielding  tissues. 

The  smaller  bladder-like  spaces  that  you  see  in  con- 
siderable numbers  in  the  substance  of  the  animal,  are 
collections  of  fluid  contained  in  excavations  of  that  sub- 
stance, which  are  called  vacuoles,  differing  from  vesicles, 
inasmuch  as  they  seem  to  have  no  proper  wall  or  inclosing 
membrane,  but  to  be  merely  casual  separations  of  the 
common  substance,  such  as  would  be  made  by  drops  of 
water  in  oil.  These  vacuoles  appear  to  be  connected  with 
the  digestive  function  ;  for  very  many  of  them  are  not 
clear,  but  are  occupied  with  granules  more  or  less  opaque, 
and  of  exceedingly  various  dimensions.  That  these  col- 
lections of  granules  are  food  you  will  see  by  the  following 
experiment. 

I  mingle  a  little  carmine  with  the  water,  just  enough  to 
impart  a  visible  tinge  to  it,  and  close  the  live-box  again. 
Already  you  perceive  that  some  of  the  tiny  globules  are 
become  turbid  and  red,  and  that  their  opacity  and  colour 
are  deepening  perceptibly.  We  see  by  this  that  the  par- 
ticles of  carmine  have  been  taken  into  the  jelly-like  sar- 
code,  and  are  accumulating  in  little  pellets  surrounded  by 
fluids,  in  these  casual  hollows  of  its  substance.  The 
process  is  rendered  still  more  obvious  when,  as  is  often 
the  case,  some  Diatomacean,*  with  a  hard  siliceous  shell, 
becomes  the  food  of  the  Amaba.  The  apparently  helpless 
jelly  spread  itself  over  the  organism,  so  as  soon  to  en- 
velop it ;  the  flesh,  which,  having  no  skin,  can  unite  with 
itself  whenever  the  parts  come  into  contact,  closes  over  the 

*  The  Diatamacece,  a  term  formed  from  the  Greek  «ii  (dia),  through, 
and  resell/  (temnein),  to  cut,  are  so  called  from  the  ease  with  which 
their  masses  may  be  broken  or  cut  through;  whence  their  popular 
name  of  brittle- worts.  They  are  usually  considered  to  belong  to  the 
vegetable  kingdom. 


382  EVENINGS    AT    THE    MICROSCOPE. 

Diatom,  which  is  thus  brought  into  the  midst  of  the 
sarcode,  a  vacuole  being  new-made  for  its  reception. 
This,  then,  performs  the  part  of  a  temporary  stomach  :  the 
digestible  portions  of  the  prey  are  extracted,  and  then  the 
insoluble  shell  of  flint  is,  as  it  were,  gradually  squeezed  to 
some  part  of  the  exterior,  and  gradually  forced  out,  the 
vacuole  disappearing  with  it,  or  perhaps  retaining  a  minute 
portion  of  the  fluid,  and  thus  perpetuating  itself  for  a  while. 
This  is  the  earliest  condition  in  which  the  process  of 
digestion  can  be  recognised. 

Another  genus  somewhat  similar  is  Arcella,  but  it  differs 
in  being  furnished  with  a  more  or  less  rounded  shell 
(lorica),  like  a  little  box.  In  examining  the  matters  that 
adhere  to  the  stems  of  duckweed,  and  other  water  plants, 
we  frequently  observe  little  circular  bodies  of  a  yellowish 
or  reddish-brown  colour,  some  much  darker  than  others, 
but  all  having  a  central  round  spot  paler  than  the  rest. 
On  first  examination  they  seem  inert  and  dead,  but  if  we 
closely  watch  one,  we  perceive  that  it  is  endowed  with  the 
power  of  motion ;  and  we  directly  discern,  thrust  out  from 
its  edge,  variable  processes,  in  the  form  of  arms,  of  clear, 
perfectly  colourless,  and  most  delicate  jelly,  sometimes 
pointed,  sometimes  blunt,  which  slowly  change  their  form 
and  position.  By  the  aid  of  these,  a  feeble  and  irregular 
motion  is  given  to  the  box,  which  is  sometimes  turned 
partly  over ;  when  we  perceive  that  its  under  side  is  flat 
or  probably  concave,  and  that  its  outline  is  cut  into  facets. 
The  lorica  is  somewhat  flexible,  for  the  edges  at  two 
opposite  points  are  sometimes  bent  down  towards  each 
other,  so  as  to  give  the  creature  the  form  of  a  crescent. 
The  internal  viscera  are  dimly  discernible  through  the 
coloured  lorica,  and  resemble  those  of  Amoeba.  A  dark 
oval  ring  is  commonly  seen  at  one  side,  which  is  probably 
the  outline  of  the  contractile  bladder.  It  may,  in  fact,  be 
considered  as  an  Amoeba,  whose  external  surface  has  the 
power  of  secreting  a  symmetrical  shell  of  horny  or 


PROTOZOA  AND  SPONGES.  388 

chitinous  substance.  The  lorica  is  about  y^th  of  an  inch 
in  diameter.  This  species  is  named  Arcella  vulgaiis. 

Laying  aside  our  live -box  with  its  contents  for  the 
present,  we  will  have  recourse  to  the  tanks  of  sea-water 
for  one  or  two  other  objects  of  intermediate  interest.  On 
the  green  and  brown  mossy  sea-weed  which  covers  the 
rocks  on  the  bottom,  you  see  many  white  specks  clinging 
to  the  filaments  ;  and  there  are  several  adhering  to  the 
sides  of  the  tank.  These  are  little  living  shelled  animals 
of  the  class  Foraminifera,  and  these  which  you  see  include 
several  species.  By  bringing  your  eye,  assisted  by  the 
lens,  to  bear  upon  one  of  these  latter,  you  perceive  that  it 
is  a  little  discoid  spiral  shell,  of  very  elegant  form, 
marked  with  curved  diverging  grooves.  This  is  the  pretty 
little  Polystomella  crispa,  a  fair  sample  of  its  class,  and 
though  not  more  than  ^th  of  an  inch  in  diameter,  it  is  a 
giant  compared  with  the  Arcella. 

There  is  more,  however,  than  the  shell  to  be  seen ; 
though  so  filmy  and  shadowy,  that  I  wonder  not  at  your 
overlooking  it.  Extending  from  two  opposite  sides  of  the 
shell  to  a  distance  each  way  considerably  exceeding  its 
diameter,  you  discern  fine  threads  of  clear  jelly,  running 
out  in  long  points.  The  power  you  employ  is  not  suffi- 
cient to  enable  you  to  resolve  their  detail :  and  for  this  I 
will  try  to  secure  a  specimen  for  the  microscope. 

In  this  other  live-box,  then,  I  inclose  one  of  the  white 
specks  from  the  moss-like  clothing  of  the  stones.  It  is, 
I  see,  of  another  species,  namely,  polymorphina  oblonga, 
but  it  will  answer  our  purpose  equally  well. 

At  present  we  see  only  the  shell,  the  removal  of  the 
animal  having  induced  it  in  alarm  to  withdraw  the  whole 
of  its  softer  parts  within  the  protection  of  its  castle.  We 
must  have  a  few  minutes'  patience. 

Now  look  again.  From  the  sides  of  the  opaque  shell 
we  see  protruding  tiny  points  of  the  clear  sarcode  ;  these 
gradually  and  slowly, — so  gradually  and  slowly  that  the 


384  EVENINGS   AT    THE   MICROSCOPE. 

eye  cannot  recognise  the  process  of  extension  —  stretch  and 
extend  their  lines  and  films  of  delicate  jelly,  till  at  length 
they  have  stretched  right  across  the  field  of  view.  The 
extension  is  principally  in  two  opposite  directions  corre- 
sponding to  the  long  axis  of  the  shell  ;  though  the  branched 
and  variously  connected  films  often  diverge  considerably  to 
either  side  of  these  lines,  giving  to  the  whole  a  more  or 
less  fan-shaped  figure. 

These  films  are  as  irregular  in  their  forms  and  sizes  as 
the  expansion  of  the  sarcode  of  Amoeba,  with  which  they 
have  the  closest  affinity.  Their  only  peculiarity  is  their 
tendency  to  run  out  into  long  ribbons  or  attenuated 
threads,  which,  however,  coalesce  and  unite  whenever  they 
come  into  mutual  contact,  and  thus  we  see  the  threads 
branching  and  anastomosing  with  the  utmost  irregularity, 
usually  with  broad  triangular  films  at  the  points  of  diverg- 
ence and  union. 

There  can  be  no  doubt  that  the  object  of  these  length- 
ened films,  which  are  termed  pseudoiwdia*  is  the  capture 
of  prey  or  food  of  some  kind  ;  perhaps  the  more  sluggish 
forms  of  minute  animalcules,  or  the  simpler  plants.  These 
the  films  of  sarcode  probably  entangle,  surround,  and  drag 
into  the  chambers  of  the  shell,  digesting  their  softer  parts 
in  temporary  vacuoles,  and  then  casting  out  the  more 
solid  remains,  just  as  the  Amceba  does. 

Though  this  beautiful  array  was  so  very  deliberately 
put  forth,  it  is,  as  you  perceive,  very  rapidly  withdrawn 
on  any  ^disturbance  to  the  animal,  as  when  we  agitate  the 
water  by  slightly  moving  or  turning  the  cover  of  the  live- 
box.  Another  fact,  of  which  you  may  convince  yourself, 
by  watching  manifest,  though  small,  changes  of  position  in 
the  shell,  while  under  observation,  is,  that  it  is  by  means 
of  the  adhesion  and  contraction  of  the  pseudopodia,  that 
the  animal  drags  itself  along  a  fixed  surface.  This  it  can 


*  Literally,  false  feet,  from  the  Greek  tyevSos  (pseudos),  a  falsehood, 
and  TOVS  (pous),  genitive  u-oSbs  (podos),  afoot. 


PROTOZOA  AND  SPONGES.  885 

effect  so  assiduously,  that  I  frequently  find  them  in  the 
morning  adhering  to  the  tank-sides  three  or  four  inches 
from  the  bottom,  though,  on  the  preyious  evening,  none 
were  visible  on  the  glass.  Thus  they  must  crawl,  on  oc- 
casion, from  a  hundred  to  a  hundred  and  fifty  times  their 
own  diameter  in  a  night. 

The  structure  of  a  Sponge  is  much  the  same  as  that 
of  these  animals,  with  the  exception  that  its  solid  part  or 
skeleton  is  not  a  continuous  covering  by  which  the  sarcode 
is  invested,  but  consists  of  fibres  or  points  or  rods  of  vary- 
ing form,  which  are  clothed  with  the  sarcode.  This  loose 
sort  of  skeleton  may  be  of  horny  or  chitinous  matter,  like 
that  of  Arcella,  or  calcareous  like  that  of  the  Foraminifera,* 
or  it  may  be  siliceous, — that  is,  composed  of  flint  (silex). 

In  some  cases,  as  in  the  common  Turkey  Sponge,  the 
horny  skeleton  consists  of  a  network  of  solid  but  slender 
fibres,  very  tough  and  elastic,  which  branch  and  anasto- 
mose in  every  direction,  at  very  short  intervals,  as  you 
may  see  by  looking  at  this  atom,  which  I  cut  off  from  a 
dressing-sponge. 

In  the  lime  and  flint  Sponges,  however,  the  continuity 
and  cohesion  of  the  skeleton  does  not  depend  upon  the 
organic  union  of  the  constituent  parts,  as  it  does  in  the 
loose  and  open  network  of  the  Turkey  sponge.  For  it  is 
made  up  of  an  immense  multitude  of  glassy  needles,  all 
separate  and  independent,  between  themselves,  yet  so  con- 
trived that  they  do  hold  together  very  firmly,  and  in  a 
great  number  of  cases  are  arranged  on  a  prescribed  plan, 
so  as  to  give  a  certain  form  and  outline  to  the  aggregate. 

If  you  have  ever  shaken  up  a  box  of  dressing-pins,  and 
have  then  endeavoured  to  take  one  out,  you  know  how  by 
their  mere  interlacement  they  adhere  together  in  a  mass, 

*  A  group  of  animals  with  shells,  resembling  in  appearance  those  of 
the  common  nautilus ;  and,  like  them,  consisting  of  several  chambers 
divided  from  one  another  by  walls  which  are  pierced  with  numerous 
minute  holes,  in  Latin  called  foramina ; — whence  their  name. 
c  c 


386  EVENINGS   AT   THE   MICROSCOPE. 

so  that  by  taking  hold  of  one  you  may  lift  a  bristling  group 
of  scores.  Somewhat  on  the  same  principle  are  the  cal- 
careous and  siliceous  pins  (spicula)  of  a  Sponge  held  to- 
gether by  mutual  interlacement.  Yet  their  cohesion  is 
aided  by  the  tenacity  of  the  living  sarcode  which  invests 
them ;  for  I  have  found  that  specimens  of  Grantia  (cal- 
careous Sponges  with  needles  of  three  rays),  when  long 
macerated  in  water,  so  that  the  sarcode  is  dissolved,  have 
very  slight  power  of  cohesion  among  their  spicula. 

To  understand  the  structure  of  a  sponge  we  will  shave  a 
thin  sectional  slice  from  this  Halichondria  suberea.  This 
when  alive  is  of  an  orange  colour ;  and  is  always  found 
closely  investing  turbinate,  or  top- shaped,  shells  which  are 
inhabited  by  Hermit-crabs.  We  will  macerate  the  slice  in 
tepid  water  for  a  quarter  of  an  hour,  and  then  examine  it 
in  the  live-box. 

The  surface  is  a  thin  layer  of  greater  density  than  any 
other  part,  and  is  composed  of  coloured  fleshy  granules, — 


SECTION  OF  SPONGE. 


omitting  for  the  present,  the  skeleton.  Of  the  same  sub- 
stance is  the  whole  slice  composed,  but  looser  and  more 
open  as  it  recedes  from  the  surface.  It  is  separated  by 


PROTOZOA  AND  SPONGES.  387 

blank  spaces  which  are  larger  towards  the  centre,  smaller 
and  more  numerous  as  they  approach  the  exterior. 

These  openings  are  sections  of  so  many  canals,  by 
which  the  whole  substance  of  a  sponge  is  permeated. 
The  surface  is  perforated  with  minute  pores,  at  which  the 
surrounding  water  enters  on  all  sides.  These  presently 
unite  into  slender  pipes,  which,  irregularly  meandering, 
are  continually  uniting  into  larger  and  yet  larger  canals ; 
of  which  the  greater  open  spaces  that  you  see  are  the 
oblique  divisions.  These  have  certain  outlets,  called 
oscula,  on  the  surface,  from  which  the  stream  is  poured 
that  has  thus  made  the  grand  tour  of  the  whole  interior. 
Such  oscula,  as  you  perceive  on  the  remainder  of  the 
Halichondria,  are  usually  raised  on  slight  eminences ;  and 
resemble,  especially  when  in  living  action,  miniature  vol- 
canoes, vomiting  torrents  of  water  and  granules  of  effete 
matter,  instead  of  fire  and  ashes. 

During  life  these  granules  were  much  more  diffused,  and 
formed  a  considerable  portion  of  the  living  flesh,  the  re- 
mainder being  composed  of  a  glairy  sarcode,  almost  fluid. 
The  whole  was  maintained  in  position  by  the  solid  spicula 
of  flint,  which  you  see  abundantly  in  this  slice.  These 
take  a  curious  form,  exactly  that  of  the  pins  which  we  use 
on  our  dressing-tables  ;  each  consisting  of  a  cylindrical 
slender  rod,  pointed  at  one  end,  and  at  the  other  sur- 
mounted by  a  globular  head,  the  whole  formed  of  glass, — 
flint  glass  literally.  You  see  them  bristling  all  round  the 
edge  of  the  section,  being  stuck  into  the  surface  of  the 
sponge,  exactly  as  pins  are  loosely  stuck  into  a  pin-cushion. 
The  heads  and  points,  too,  project  into  the  cavities;  more, 
however,  than  they  did  during  life,  for  you  must  make 
allowance  for  the  shrinking  of  the  soft  parts ;  and  thus 
you  perceive  how  the  whole  structure  is  permeated  by 
these  glassy  pins,  which  seem  to  be  entangled  together 
quite  at  random  without  rule  or  arrangement.  And  yet 
there  is  an  arrangement  discernible  here ;  for  the  canals 
cc  2 


388  EVENINGS    AT    THE    MICROSCOPE. 

are  formed  by  the  manner  in  which  these  are  grouped  ; 
and  this  is  seen  much  more  clearly  in  the  case  of  the  three- 
rayed  needles  of  lime  in  the  Gr antics.  Mr.  Bowerbank  has 
shown  that  in  G-.  compressa  the  substance  is  divided  into 
very  regular  chambers  in  a  double  series,  divided  by  A 
diaphragm,  whose  axis  is  at  right  angle.8  to  the  axis  of  the 
sponge  ;  and  that  these  chambers  are  defined  by  walls 
made  tfp  of  the  three-rayed  needles  in  their  mutual  inter- 
lacement. 


INFUSORIA.  389 


CHAPTER  XXI. 

INFUSORIA. 

WE  will  now  resume  our  examination  of  the  drop  of  pond- 
water,  and  the  fragments  of  Myriophyllum,  which  have 
been  waiting  far  us  in  the  live-box. 

Our  attention  then  shall  first  be  given  to  some  elegant 
creatures  of  a  brilliant  translucent  green  hue,  which  are 
gracefully  gliding  about.  They  are  of  the  genus  Euglena, 
so  called  because  each  is  furnished  with  a  very  conspicuous 
spot  of  a  clear  red  hue,  situated  near  the  head,  which 
Ehrenberg,  on  account  of  its  resemblance  to  the  lowest 
forms  of  eyes  in  the  Rot  if  era,  that  are  somewhat  similar  in 
colour  and  appearance,  pronounced  to  be  an  organ  of 
vision.  More  recent  physiologists,  however,  doubt  the 
correctness  of  the  conclusion. 

The  animals  are  of  several  kinds.  The  most  numerous 
is  an  active  little  thing  of  about  ^J-oth  of  an  inch  in  length 
when  extended,  though  from  its  extreme  versatility  it  is  as 
difficult  to  assign  to  it  a  definite  size  as  a  definite  shape. 
It  seems  to  be  the  E.  sanguinea,  so  called  because  it  is 
said  to  occur  sometimes  of  a  deep  red  hue,  and  in  such 
vast  profusion  as  to  give  the  waters  the  appearance  of 
blood.  I  have  never  seen  it,  however,  other  than  as  it 
now  appears,  rich  emerald  green  in  the  body,  with  the  two 
extremities  perfectly  clear  and  colourless.  I  might,  per- 
haps, describe  its  ordinary  form  as  spindle-shaped,  with  a 
pointed  tail,  and  a  blunt,  rounded  head  ;  but  it  is  remark- 
able for  the  variableness  of  its  shape.  It  is  capable  of 


890  EVENINGS   AT    THE   MICROSCOPE. 

assuming  an  appearance  very  diverse  from  what  it  had  half 
a  minute  before,  so  that  you  would  hardly  identify  it,  if 
you  were  not  watching  its  evolutions.  Whether  this  ability 
to  prove  an  alias  be  at  all  dependent  on  the  remarkable 
clear-headedness  of  the  subject,  I  leave  for  those  who  are 
skilled  in  metaphysics  to  determine.  Away  they  go, 
tumbling  over  and  over,  revolving  on  the  long  axis  as  they 
proceed,  which  they  do  not  very  rapidly,  with  the  blunt 
extremity  forward. 

Here -is  another  form,  a  little  larger  than  the  former, 
but  much  more  slender ;  yet  from  the  slowness  and  steadi- 
ness of  its  movement  more  easy  of  observation.  It  is 
named  E.  acus,  or  "the  Needle  Euglena."  This  is  an 
animalcule  of  great  elegance  and  brilliancy ;  its  sparkling 
green  hue,  with  colourless  extremities,  and  its  rich  pale 
ciimson  eye,  are  very  beautiful.  It  commonly  swims  ex- 
tended, with  a  slow  gliding  motion,  turning  round  on  its 
long  axis  as  it  proceeds,  as  may  be  distinctly  seen  by  the 
rotation  of  certain  clear  oblong  substances  in  its  body. 
These,  then,  are  seen  not  in  the  interior,  but  near  the 
surface,  as  they  would  appear  if  imbedded  in  the  flesh 
around  a  hollow  centre.  The  interior  is  probably  not 
hollow,  but  occupied  with  pellucid  sarcode.  These  were 
assumed  by  Ehrenberg,  but  on  no  adequate  grounds,  to 
be  organs  connected  with  reproduction.  They  vary  in 
number  in  different  individuals,  and  those  which  contain 
the  greatest  number  are  thereby  more  swollen.  They 
appear  to  be  separated  into  two  series,  one  anterior,  the 
other  posterior.  The  animal  is  capable  of  bending  its 
head  and  body  in  various  directions,  but  is  most  beautiful 
when  straight.  The  front  is  furnished  with  a  slender 
thread-like  proboscis.  This  species  affords  us  a  good 
opportunity  of  observing  the  red  spot,  which,  for  con- 
venience sake,  we  may  still  term  an  eye.  It  seems  to  be 
an  irregular  oblong  vacuole,  or  excavation  in  the  sarcode, 
filled  with  a  clear  ruby-red  fluid.  The  red  spot  in  the 


INFUSORIA.  891 

Eotifera  is  connected  with  a  well-defined  crystalline  lens, 
whose  definite  form  and  high  refractive  power  may  in 
many  cases  be  distinctly  marked  ;  but  here  nothing  of  the 
kind  is  seen;  the  spot  itself  has  no  certain  shape,  and 
does  not  appear  to  be  bounded  by  a  proper  wall.  Some 
forms,  which  are  by  general  consent  admitted  to  be  plants, 
have  similar  spots;  and  hence  it  has  been,  rather  too 
hastily,  I  venture  to  think,  concluded  that  they  have  no 
connexion  with  vision.  I  think  it  still  possible  that  a  sen- 
sibility to  the  difference  between  light  and  darkness  may 
be  the  function  of  the  organ. 

I  have  found  that  this  animal,  when  allowed  to  dry  on 
a  plate  of  glass,  retains  its  form  and  colour  perfectly  ;  but 
in  about  two  days  the  eye-spot,  which  at  first  becomes 
much  larger  in  the  drying,  gradually  loses  all  traces  of 
its  brilliant  colour,  probably  by  the  evaporation  of  the 
contained  fluid. 

Another  pretty  species  you  see  gliding  along  among  the 
rest,  called  E.  triquetra,  or  the  Three-sided.  It  bears  a 
resemblance  to  a  broad  rounded  leaf,  with  the  foot-stalk 
forming  a  short  transparent  point,  and  the  mid-rib  ele- 
vated into  a  sharp  ridge.  The 
under  side  seems  slightly  concave. 
This  is  equally  attractive  with 
the  others.  It  is  persistent  in 
form,  and  appears  not  to  be 
even  flexible.  Its  motion  is  slow, 
and  as  it  goes,  it  rolls  irregularly 
over  and  over  in  all  directions, 
not  revolving  on  its  long  axis,  and 
thus  giving  you  very  satisfactory  views,  though  only 
momentary,  of  the  keel  with  which  the  back  is  furnished. 
It  is  in  the  turnings  of  such  minute  creatures  that  the 
microscopist  often  gets  a  glimpse  of  peculiarities  of  form, 
which  a  view  of  the  animal  when  in  repose,  however  long 
continued,  fails  to  reveal.  Longitudinal  interrupted  lines 


THREB.8IDKD 


392  EVENINGS    AT    THE    MICROSCOPE. 

are  seen  running  down  the  body  of  this  pretty  leaf,  which 
do  not  appear  to  mark  irregularities  of  the  surface,  and 
therefore  are  probahly  internal.  Ehrenberg  calls  these 
and  similar  collections  of  granules  "  ova,"  or  eggs  ;  but 
this  is  to  cut  the  knot  instead  of  untying  it.  There  is  no 
sufficient  reason  to  believe  that  these  animals  increase  by 
ova. 

About  the  front  of  all  these  Euglena,  you  may  discern 
now  and  then  a  slight  flickering  or  quivering  in  the  water. 
The  power  we  are  using,  though  best  for  the  general 
display  of  the  form,  is  insufficient  to  resolve  this  appear- 
ance :  I  will  put  on  a  higher  objective.  You  now  see  that 
there  proceeds  from  the  frontal  part  of  the  body  a  long 
and  very  slender  filament,  which  is  whisked  about  in  the 
manner  of  a  whip -lash.  This  is  considered  to  be  the 
organ  of  locomotion ;  but  I  rather  doubt  that  such  is 
the  function ;  the  smooth  and  even  gliding,  often  rotating, 
action  of  the  creature,  seems  more  like  that  produced  by 
minute  and  generally-distributed  cilia,  than  that  caused 
by  the  lashings  of  a  single  long  thread. 

Yet  two  more  species  of  this  extensive  genus  we  dis- 
cern in  this  well-stocked  drop  of  water.  They  have 
received  the  appellations  of  the  Pear  (E.  pyrum)  and  the 
Sloth  (E.  deses).  The  former  is  the  most  minute  we  have 
yet  seen  and  seems  to  be  scarce ;  but  it  is  highly  curious 
and  interesting  in  appearance.  It  much  resembles  in 
outline  a  fish  of  the  genus  Balistes;  the  muzzle  being 
somewhat  protruded  and  truncate,  and  the  form  rhom- 
boidal ;  it  terminates  in  a  slender  pointed  tail.  The  body 
is  obliquely  fluted,  which  gives  a  very  singular  effect ;  for 
from  the  transparency  of  the  tissues  the  lines  of  the 
opposite  side  can  be  discerned  crossing  those  next  the 
eye,  and  dividing  the  animal  into  lozenge -shaped  areas. 
The  colour  is  sparkling  green,  but  the  tail  and  the  edges 
of  the  body  are  clear  and  colourless,  and  there  is  a  bright 
red  eye.  At  other  times  this  Euglena  takes  the  form  of  a 


INFUSORIA.  898 

claret-bottle  or  an  oil-flask ;  the  muzzle  being  broadly 
truncate  or  even  indented. 

Its  motion  is  rapid :  a  swift  gliding  in  the  direction  of 
its  long  axis ;  it  turns  continually  on  the  same  axis,  which 
gives  a  waving  irregularity  to  its  course,  and  has  a  pretty 
effect  from  the  continual  crossing  of  the  flutings  in  the 
revolving.  This  specimen  is  about  y^th  of  an  inch  in 
length,  including  the  tail. 

Euglena  deses  is  much  larger,  being  about  u^th  of  an 
inch  in  length,  though  the  tail  is  very  short.  It  has  a 
thick  body,  with  a  round,  blunt  head  ;  it  tapers  suddenly 
to  the  tail.  Its  colour  is  bright  green  with  a  red  eye ; 
but  the  presence  of  an  infinite  number  of  irregular  oblong 
granules  and  lines  with  several  globular  vesicles,  gives  an 
opacity  and  a  blackness  to  its  appearance.  In  its  manners 
it  is  sluggish;  it  never  swims  or  glides  gracefully  and 
swiftly  among  its  playful  companions,  but  contents  itself 
with  twining  slowly  among  the  downy  stems  and  filaments 
of  the  water-plants,  or  crawls  upon  the  surface  of  the  live- 
box.  It  does  not  appear  to  change  its  form,  otherwise 
than  its  soft  and  flexible  body  necessitates,  as  it  twines 
about. 

But  enough  of  the  Euglenas.  For  I  have  just  caught 
sight  of  a  much  more  curious  creature,  the  Swan  Animal- 
cule (Trachelocerca  olor).  It  is  reposing  on  one  of  the 
leaves  of  the  Myriophyllum,  its  long  and  flexible  neck 
lengthening  and  contracting  at  pleasure,  the  tip  thrown 
about  in  quick  jerks  in  every  direction,  somewhat  like  a 
caterpillar  when  it  touches  several  points  impatiently  with 
its  head. 

If  we  admire  the  graceful  sailing  of  a  swan  upon  a  lake, 
the  swelling  of  its  rounded  bosom,  the  elegant  curves  of 
its  long  neck,  we  shall  be  struck  with  the  form  and  motion 
of  this  animal.  The  form  has  much  resemblance  to  that 
of  a  swan,  or  still  more  to  that  of  a  snake-bird  (Plotus) ; 
the  body,  swelling  in  the  middle,  tapers  gradually  into  a 


394  EVENINGS    AT    THE    MICROSCOPE. 

slender  pointed  tail  at  one  extremity,  and  at  the  other  into 
a  very  long  and  equally  slender  neck,  which  is  terminated 
by  a  slight  dilatation.  The  whole  is  perfectly  transparent, 
but  the  body  is  filled  with  numerous  minute  globular 
vessels,  or  temporary  stomachs.  The  grace  of  its  motion, 
as  it  glides  along  with  a  free  and  moderately  swift  pro- 
gression through  the  clear  water,  or  winds  through  the 
intricate  passages  of  the  green  conferva,  throwing  its  long 
jieck  into  elegant  curves,  is  very  remarkable.  There  are, 
I  see,  two  of  them,  which,  however,  take  no  notice  of  each 
other,  even  when  passing  close  to  each  other ;  the  neck  of 


SWAN-NECK  AND  ITS  DIVISIONS. 

one  is  much  longer  than  that  of  the  other.  Now  and 
then,  when  gliding  along,  the  neck  is  suddenly  contracted, 
but  not  wholly,  as  if  something  had  alarmed  or  displeased 
the  animal ;  the  body  also  can  be  swollen  or  lengthened 
at  pleasure  ;  it  can  move  in  either  direction,  but  the  neck 
usually  goes  foremost,  extended  in  the  direction  of  the 
motion,  and  seems  to  be  used  to  explore  the  way. 

I  had  once  an  opportunity  of  seeing  the  process  of 
increase  by  spontaneous  self- division  in  this  creature.  It 
was  an  unusually  large  specimen,  found  in  an  old  infusion 
of  sage  leaves.  When  I  discovered  it,  it  was  darting 
about  its  long  neck  in  the  most  beautiful  contortions.  As 
it  was  partly  hidden  by  the  vegetable  fibre  present,  I 


INFUSORIA.  895 

turned  the  glass  cover  so  as  to  alter  the  position  of  the 
contents.  On  again  looking,  the  Swan  was  in  a  clear  part 
of  the  field,  but  in  the  form  of  a  dark  globose  mass,  the 
neck  being  entirely  contracted.  It  was  quite  still,  except 
a  continual  slight  alteration  of  the  form  by  the  protrusion 
or  contraction  of  parts  of  the  outline.  The  body  seemed 
full  of  minute  globules,  set  in  a  granular  mass  of  a 
blackish  hue,  and  the  outline  was  not  a  continuous  line, 
but  formed  a  multitude  of  rounded  elevations.  Presently 
it  protruded  the  clear  neck,  but  only  for  a  short  distance, 
and  then  retracted  it  as  before  ;  when  the  only  indication 
of  the  presence  of  this  organ  was  a  depression  in  one 
part  of  the  surface,  somewhat  like  the  mouth  of  a  closed 
Actinia,  where  there  was  a  slight  but  incessant  working, 
very  much  like  the  irregular  motion  on  the  surface  of 
boiling  water,  in  miniature ;  there  was  also  an  indistinct 
ciliary  action  at  this  part,  not  of  rotation,  nor  of  vibration, 
but  a  sort  of  waving.  At  this  point  I  had  occasion  to  get 
up  from  the  table,  and  though  I  was  not  away  more  than 
a  minute,  on  my  return  I  observed  a  strong  constriction 
around  the  middle  of  the  body.  It  was  transverse,  for 
the  depressed  and  ciliated  mouth  was  at  a  point  exactly  at 
right  angles  to  the  constriction.  From  the  depth  to  which 
this  latter  extended  in  so  few  minutes,  I  supposed  the 
process  of  separation  would  be  very  rapid ;  for  I  could 
very  soon  see  a  line  of  light  all  across  at  intervals,  and 
the  two  halves  seemed  to  slide  freely  on  each  other.  Yet 
they  remained  long  without  much  apparent  progress,  or 
even  change,  except  that  the  anterior  half  at  one  tune 
threw  forth  its  neck  a  short  distance  ;  at  this  time  it 
looked  extremely  like  a  bird,  bridling  up  its  lithe  neck  and 
swelling  bosom;  while,  to  make  the  resemblance  perfect, 
it  began  to  imitate  the  action  of  a  fowl  picking  up  grain, 
bobbing  its  head  hither  and  thither :  so  curious  are  the 
analogies  of  nature  !  Along  the  dividing  line  there  had 
appeared  very  early  in  the  posterior  half  a  distinct  ciliary 


396  EVENINGS    AT    THE    MICROSCOPE. 

action ;  after  a  while  (how,  I  do  not  exactly  know),  with- 
out the  general  relation  of  position  being  changed,  the 
mouth  of  the  anterior  (which  must  now  be  called  the  old) 
animal  appeared  on  the  side,  and  at  the  point  corre- 
spondent in  the  other,  a  similar  ciliary  wreath  appeared, 
while  the  action  along  the  dividing  line  was  no  longer 
seen.  So  that  the  division  which  was  at  first  transverse 
now  appeared  longitudinal.  I  believe,  however,  the  ani- 
mals were  really  separated  before  this,  though  they  re- 
mained in  contact,  for  as  they  slid  over  each  other  it  was 
manifest  that  each  had  an  independent  action. 

At  length  about  an  hour  and  a-half  after  the  first 
appearance  of  the  constriction,  the  new  animal  threw  out 
its  clear  neck  to  a  great  length,  writhing  it  about  with 
rapid  agility,  and  forming  the  most  elegant  curves,  like 
those  of  a  serpent,  often  completely  encircling  its  own 
body  with  it.  It  still  remained,  however,  in  contact  with 
its  parent,  which  after  a  time  also  protruded  its  neck  in 
the  same  manner.  Both  then  retracted  and  remained  still 
for  a  while  ;  and  again,  almost  simultaneously  threw  out 
their  long  necks  and  then  retired  to  sluggish  repose. 

Among  the  sediment,  the  grains  of  which  are  driven 
hither  and  thither  by  their  spasmodic,  jerking  movements, 
you  see  several  individuals  of  another  sort  of  creature, — 
the  Chrysalis  Animalcule  (Paramcecium  aurelia).  This  is 
a  "  Triton  among  minnows;  "  for  it  is  greatly  larger  than 
any  of  those  we  have  yet  observed,  and  is  just  visible  to 
the  naked  eye,  when  we  hold  up  the  live-box  obliquely 
against  the  light ;  for  then  the  animals  appear  as  the 
smallest  possible  white  specks. 

Bringing  them  again  under  the  microscope,  each  pre- 
sents a  pellucid  appearance,  and  an  oblong  figure,  of  which 
the  fore  part  is  somewhat  narrowed.  The  back  rises  in  a 
rounded  elevation,  and  the  mouth  is  situated  as  far  back 
as  the  middle  of  the  body  upon  the  under  surface,  where 
its  position  is  marked  by  a  sort  of  long  fold,  the  sides  of 


INFUSORIA.  897 

which  are  fringed  with  long  cilia,  whose  vibrations  are  very 
marked.  The  whole  surface,  on  both  sides,  is  covered 
with  minute  cilia,  arranged  in  longitudinal  rows,  of  which, 
according  to  the  great  Prussian  professor,  there  are  from 
thirty  to  sixty  on  each  surface,  each  row  bearing  sixty  or 
seventy  cilia.  This  must  be  considered  as  an  approxima- 
tion ;  for  we  may  well  doubt  the  accuracy  of  the  counting, 
when  the  objects  are  so  very  evanescent  as  these  vibrating 
cilia. 

The  vacuoles,  and  the  temporary  stomachs,  more  or  less 
completely  filled  with  the  brown  and  green  food,  which  the 
animals  are  collecting  from  the  decayed  vegetable  matters, 
are  sufficiently  numerous  and  conspicuous  ;  but  they  may 
be  rendered  still  more  so  by  the  device  of  mixing  a  little 
carmine  with  the  water.  The  ciliary  currents  are  thus 
instantaneously  rendered  strikingly  visible.  The  crimson 
atoms  are  attracted  from  all  quarters  towards  the  tail  of  the 
animal,  whence  they  are  urged  in  a  rapid  stream  along  one 
side  towards  the  head,  around  which  they  are  hurled,  and 
then  down  the  other  side  to  the  tail,  pouring  off  in  a  dense 
cloud  in  a  direction  contrary  to  that  in  which  they  origi- 
nally approached. 

But  now  the  gathered  currents  have  produced  their  ex- 
pected result ;  for  many  of  the  globular  vacuoles  are  already 
become  of  a  beautiful  rosy  hue,  from  the  minute  particles 
of  the  pigment  which  have  been  whirled  to  the  mouth,  and 
swallowed. 

The  feature  of  greatest  interest,  however,  in  this  animal 
is  the  contractile  bladder.  Two  of  these  organs  are 
usually  seen  co-existent  in  each  individual,  placed,  the 
one  on  the  front,  the  other  in  the  rear  of  the  mouth, 
but  near  the  opposite, — i.e.,  the  dorsal,  surface  of  the 
body  ;  for  as  the  creature  slowly  revolves  on  its  longitu- 
dinal axis,  the  line  of  the  vesicles  alternately  approaches 
and  recedes  from  that  of  the  mouth.  They  are  remarkable 
for  their  structure.  Far  from  the  simplicity  in  which  the 


398  EVENINGS    AT    THE    MICROSCOPE. 

organ  is  usually  presented  to  us  in  the  animals  of  this 
class,  the  contractile  bladders  are  here  very  complex. 
Each  when  distended  is  globular  ;  and  it  is  surrounded  by 
a  number  of  others  of  much  smaller  dimensions,  and  of  a 
drop-like  form,  so  set  as  to  radiate  around  the  principal 
vesicle  as  a  centre,  the  rounded  portion  of  each  in  apparent 
contact  with  the  vesicle,  and  the  slender  extremity  run- 
ning off  as  an  attenuated  point  till  lost  to  sight  in  the 
sarcode.  The  main  vesicles  alternately  become  distended, 
and  suddenly  contract  to  a  point ;  while  the  radiating  cells 
are  continually  varying  in  size,  though  in  a  less  degree. 
It  is  customary  to  describe  the  secondary  vesicles  as  coming 
into  view  at  the  instant  of  the  contraction  of  the  primary 


PABAMCECIUM. 


one,  and  to  suppose  that  the  emptying  of  the  one  is  the 
filling  of  the  other,  but  I  have  not  been  able  to  observe 
this  mutual  relation  satisfactorily  made  out.  The  smaller 
as  well  as  the  larger  vesicles  are  conspicuous  from  their 
colourless  transparency ;  for  the  general  sarcode  of  the 
body,  though  pellucid,  is  only  so  in  the  same  degree  as 
glass,  slightly  smoked ;  besides  that  its  clearness  is  often 
impaired  by  crowds  of  granules  and  minute  globules. 

You  ask  what  is  that  comparatively  large  oval  body 
attached  by  its  side  to  one  of  the  leaves  of  the  plant.  It 
is  the  egg  of  some  considerable  Rotifer,  probably  Euchlanis, 
which  is  always  glued  to  some  filament  or  stem  of  a  water- 
plant.  It  may  interest  you  to  watch  the  progress  of  the 
contained  embryo,  which  you  can  readily  do,  since  the  egg- 
shell is  as  transparent  as  glass,  and  the  infant  animal 
already  displays  the  movements  of  independent  life.  Mean- 


INFUSOBIA.  399 

while  I  will  tell  you  the  tragical  and  lamentable  history  of 
just  such  an  embryo  as  this,  that  was  eaten  up  before  it 
was  born,  under  my  own  eye.  One  of  the  depredators  was 
a  very  amusing  animalcule,  which  is  sufficiently  scarce  to 
make  its  occurrence  a  thing  of  interest,  especially  to  a 
young  microscopist,  as  I  was  at  the  time. 

A  large  egg  of  (as  I  believe)  Euchlanis  dilatata  had  been 
laid  during  the  night  on  a  leaf  of  Nitella,  in  the  live-box. 
When  I  observed  it,  the 
transparency  of  the  shell 
allowed  the  inclosed  ani- 
mal to  be  seen  with  its  ^m&&vv<?'"FEK  <--  <-^*  /ez-, 

.  .    ,  .  ^^.dafe.  'wi.'yr^^  (jMBk^l^ 

viscera,  which  occasion-     ^^aH  HMBfe>^^^ 
ally  contracted  and  ex-       *®  m .  <& 


CHILOMONA8> 


panded  ;  the  place  of  the 
mastax  I  could  distinctly 
make  out.  The  cilia  were 
vibrating,  not  very  ra- 
pidly, but  constantly,  on 
the  front,  where  there 
was  a  vacant  space  between  the  animal  and  the  shell. 
From  seven  A.M.  when  I  first  saw  it,  I  watched  it  for  about 
eight  hours,  without  perceiving  any  change  ;  but  at  that 
hour  having  withdrawn  for  a  short  time,  I  perceived  on  my 
return  that  a  portion  of  the  animal  was  outside  the 
shell.  The  appearance  was  that  of  a  small  colourless 
bladder  oozing  out  at  an  imperceptible  aperture  ;  and  this 
oval  vesicle  quickly  but  gradually  increased,  until  it  was 
half  as  large  as  the  egg  itself.  A  little  earlier  than  this 
point,  the  cilia  were  seen  on  the  front  or  lower  side  of  the 
excluded  portion,  and  these  began  to  wave  languidly  in  a 
hooked  form.  They  thus  seemed  much  longer  and  more 
substantial  than  when  rotating  in  the  perfect  animal. 
When  excluded  to  the  extent  just  named,  some  little  crea- 
tures that  were  flitting  about  found  it,  and  began  to 
assemble  round  it.  These  were  far  too  rapid  in  their 


400  EVENINGS    AT    THE    MICROSCOPE. 

movements  to  allow  me  to  identify  them  before,  or  to  per- 
ceive anything  else  than  their  swift  motion  and  oval  form  ; 
but  this  attraction,  causing  them  to  become  still,  allowed 
me  to  perceive  their  singular  and  beautiful  structure.  Each 
consists  of  an  oval  vase  open  at  the  top,  the  margin  of 
which  is  cut  into  a  number  of  little  points  ;  the  sides  are 
marked  by  a  series  of  ribs,  which  run  down  longitudinally, 
and  are  crossed  by  other  transverse  ones;  the  rounded 
bottom  is  furnished  with  three  short  points,  so  that  the 
whole  reminded  me  of  a  barrel  with  its  staves  and  hoops, 
set  on  a  three-legged  stool.  Within  the  body,  which  is 
colourless,  are  seen  small  dark  spots  which  are  probably 
the  stomach-vacuoles.  Thus  I  identified  these  little  barrels 
with  Coleps  hirtus  of  Ehrenberg,  but  I  found  no  record  of 
their  carnivorous  propensities.  One  aftec  another  whirled 
into  the  field,  and  after  a  few  gyrations  became  stationary 
at  the  head  of  the  half-born  Euchlanis,  just  as  I  have  seen 
vultures  gather  one  by  one  to  a  carcase.  Very  soon  there 
were  a  dozen  or  fifteen  of  them,  some  of  which  were  ever 
shifting  their  places,  and  some  were  playing  around,  or 
revolving  on  their  longitudinal  axes.  I  found  that  their 
object  really  was  to  prey  on  the  soft  parts  of  the  creature 
just  excluded  from  the  egg ;  for,  by  carefully  watching  one, 
I  distinctly  perceived  particles  of  the  flesh  fly  off,  as  it 
were,  and  disappear  in  the  body  of  the  Coleps.  The 
appearance  was  that  of  steel  filings  drawn  to  a  magnet,  for 
the  mouth  of  the  Coleps  was  not  in  actual  contact  with  the 
flesh  ;  and  therefore,  I  suppose,  the  surface  having  been  in 
some  way  ruptured  (which  I  could  see  it  was),  the  loose 
gelatinous  atoms  were  sucked  off  by  a  strong  ciliary  cur- 
rent. They  did  not  attack  any  other  part,  and  after  having 
continued  their  murderous  occupation  about  ten  minutes, 
they  one  by  one  departed.  The  ciliary  motion  of  the 
Euchlanis  ceased  immediately  after  it  was  first  attacked, 
and  I  suppose  it  was  soon  killed,  for  it  did  not  increase  in 
size  in  the  least  afterwards.  When  the  Colepes  left  it,  a 


INFUSORIA.  401 

great  portion,  perhaps  a  third,  of  the  excluded  parts  was 
devoured. 

As  soon  as  the  depredators  were  gone,  or  even  before, 
others  more  diminutive,  but  more  numerous,  were  ready 
to  take  their  place.  The  drop  of  water  under  review  had 
been  found  amazingly  full  of  a  small  oval  Monas,  perfectly 
transparent,  of  an  oval  form,  with  some  granules  visible  in 
the  interior.  They  were  about  ^uVjrth  of  an  inch  in  length. 
They  filled  the  whole  field,  gliding  about  very  nimbly,  but 
so  close  as  but  just  to  allow  space  for  motion,  and  that  in 
several  strata.  By  the  morning  these  were  collected  in 
masses,  which  to  the  naked  eye  looked  like  little  undefined 
white  clouds,  but  which  under  the  microscope  showed  the 
Monads  in  incalculable  multitudes,  but  for  the  most  part 
in  still  repose.  Some  were  seen  moving  to  and  fro,  how- 
ever, and,  in  the  course  of  the  day,  most  of  them  became 
again  active.  As  soon  as  the  Colepes  had  forsaken  their- 
prey,  the  Monads  began  to  gather  round  it,  cleaving  to  the 
same  parts,  and  apparently  imbibing  the  juices,  for  the 
extruded  parts  still  slowly  decreased,  until  at  length  these 
were  reduced  to  about  one-third  of  their  original  di- 
mensions. 

A  close  examination  of  these  latter  when  they  had 
settled  to  rest  showed  me  that  they  were  of  the  species 
Chilomonas  paramcecium.  There  is  an  indentation  on  one 
side  of  the  front  where  the  mouth  is  situated :  here  there 
is  a  ciliary  action ;  the  projecting  part,  called  the  Up,  is 
said  to  be  furnished  with  two  slender  flexible  proboscides, 
but  my  power  was  not  sufficient  to  discern  any  trace  of 
these.  A  sort  of  a  ridge,  or  keel,  runs  down  the  length  of 
the  body,  perceptible  by  a  slight  line  ;  numbers  of  stomach- 
cells  also  are  perceptible.  The  motion  of  these  lip-monads 
was  not  very  rapid  when  unexcited ;  it  is  performed  by  a 
sort  of  lateral  half-roll,  the  two  sides  alternately  being 
turned  up,  like  a  boat  broadside  to  a  swell,  and  the  line  of 
progression  is  undulating. 

D  D 


402 


EVENINGS    AT    THE    MICROSCOPE. 


And  now,  having  pretty  well  exhausted  the  contents  of 
this  live-box,  let  us  try  a  dip  from  this  other  phial  from 
another  locality,  equally  productive,  if  I  am  not  mistaken. 
Yes  ;  for,  to  begin,  the  stalks  of  Nitella  here  are  fringed 
with  populous  colonies  of  the  most  attractive  of  all  the 
Infusoria,  the  beautiful  Vorticella.  The  species  is  not  the 
common  bell-shaped  one,  but  the  smaller  with  pursed 
mouth,  the  little  V.  microstoma. 

Look  at  this  active  group,  consisting  of  a  dozen  or  so 
of  glassy  vases,  shaped  something  like  pears,  or  elegant 


antique  urns,  elevated  on  the  extremities  of  long  and  very 
slender  stalks,  as  slender  as  threads,  and  about  six  times 
as  long  as  the  vases.  The  stalks  grow  from  the  midst  of 
the  floccose  rubbish  attached  to  the  plant,  and  diverge  as 
they  ascend,  thus  carrying  their  lovely  bells  clear  of  one 
another. 

Each  vase   is    elegantly  ventricose,  or  swollen,  in  the 


INFUSORIA.  408 

middle,  terminating  below  in  a  kind  of  nipple  to  which  the 
stalk  is  attached,  and  above  in  a  short  wide  neck  with  a 
thickened  rim.  This  last  is  highly  sensitive  and  con- 
tractile ;  its  inner  edge  is  set  round  with  a  circle  of 
vibratile  cilia,  which,  when  in  full  play,  produce  a  pair  of 
small  circular  whirlpools  over  two  opposite  points  of  the 
brim.  The  cilia  themselves  cannot  be  distinguished,  but 
their  optical  expression  is  curious.  At  the  two  opposite 
points  of  the  circular  margin,  as  seen  in  perspective  when 
slightly  inclined  towards  the  observer,  viz.,  at  those  points 
where  the  cilia,  from  their  position  with  regard  to  the  eye, 
would  be  crowded  together,  there  are  seen  two  dark 
dashes,  representing,  doubtless,  two  ciliary  waves,  but 
which  have  all  the  appearance  of  tangible  objects,  some- 
times withdrawn,  sometimes  protruded,  and  often  vibrated 
with  a  rapid  snatching  movement. 

These  vases  are  of  the  usual  appearance  in  Infusoria. 
Their  substance  is  the  clear  transparent  colourless  sarcode, 
but  it  contains  within  it  more  or  less  of  the  cloudy  nebulous 
matter  which  we  have  been  lately  familiar  with.  There 
are  several  globular  vesicles  or  vacuoles,  some  ready  to 
imbibe  colour  from  pigment,  and  others  already  occupied 
with  brown  food;  while  in  each  case  we  see,  near  the 
centre  of  the  vase,  a  longish  body  of  clear  granular  texture, 
which  is  called  the  nucleus,  and  which  seems  to  play  an 
essential  part  in  the  vital  economy  of  the  animal. 

The  movements  of  a  group  such  as  that  we  are  looking 
at  are  very  sprightly  and  pleasing.  The  vases  turned  in 
all  directions,  some  presenting  their  mouths,  some  their 
sides,  some  their  bases,  to  the  eye  ;  inclined  at  various 
angles  from  the  perpendicular,  and  bending  in  diverse 
degrees  upon  the  extremity  of  their  stalks ;  swaying  slowly 
and  gracefully  to  and  fro,  as  driven  hither  and  thither  by 
the  ciliary  currents ;  and,  above  all,  ever  flying  up  and 
down  within  the  length  of  their  radius,  as  a  bird  when 
confined  by  a  string ; — all  these  circumstances  impart  a 
D  D  2 


404  EVENINGS   AT    THE    MICROSCOPE. 

charm  to  this  elegant  animalcule,  which  enables  us  to  look 
long  at  it  without  weariness. 

This  last  movement  is  peculiar,  and  worthy  of  a  moment's 
closer  examination.  The  stalk,  when  extended  to  the 
utmost,  is  an  elastic  glassy  thread,  nearly  straight,  like  a 
wire,  but  never  so  absolutely  straight  as  not  to  show 
slight  undulations.  The  stalk,  when  thus  drawn  tight, 
is  highly  sensitive  to  vibrations  in  the  surrounding  medium  ; 
and  as  in  the  circumstances  in  which  we  observe  the 
animals,  such  vibrations  must  be  every  instant  communi- 
cated to  the  vessel  in  which  they  are  confined,  the  stalks 
are  no  sooner  fully  extended  than  they  contract  with  alarm. 
This  depends  on  a  contractile  cord  which  passes  throughout 
the  entire  length  of  the  stalk,  and  which  is  distinctly  visible 
in  the  larger  species  as  a  narrow  band.  We  can  scarcely 
err  in  considering  this  ribbon  as  a  rudimentary  condition 
of  muscle,  though  we  do  not  recognise  in  it  some  of  the 
characteristic  conditions  which  we  are  accustomed  to  see 
in  it  in  higher  animals. 

The  contraction  of  the  muscle  is  very  sudden,  energetic, 
and  complete.  With  a  rapidity  which  the  eye  cannot 
follow,  the  vase  is  brought  down  almost  to  the  very  base 
of  the  stalk.  Then  it  slowly  rises  again  ;  and  now  we  see, 
what  we  could  not  discern  in  the  act  of  contraction  itself, 
that  in  that  act  the  stalk  was  thrown  into  an  elegant  spiral  of 
many  turns,  which  at  the  utmost  point  of  contraction  were 
packed  close  on  each  other,  but  which  in  the  extending  act 
gradually  separate,  and  at  length  straighten  their  curves. 

In  any  stage  of  the  extension,  the  sudden  contact  of 
the  vase  with  any  floating  or  fixed  object  apparently  causes 
alarm,  and  induces  the  vigorous  contraction ;  but  vibra- 
tions, even  when  so  violent  as  those  produced  by  tapping 
the  stage  of  the  microscope  with  the  finger-nail,  have  no 
effect  unless  the  stalk  be  tense,  its  own  power  of  vibration 
being  then  only  developed,  just  as  a  cord  becomes  musical 
in  proportion  to  its  tension. 


INFUSORIA.  405 

It  is  not  until  we  view  these  creatures  with  a  good 
microscope  that  we  acquire  an  adequate  idea  of  their 
beauty :  for  myself,  at  least,  it  was  so.  I  had  seen  en- 
gravings of  many  of  the  invisible  animalcules,  and  had 
read  technical  descriptions  ;  but  of  their  brilliant  transpa- 
rency, their  sudden  and  sprightly  motions,  their  general 
elegance  and  delicacy,  and  the  apparent  intelligence  with 
which  they  are  endowed,  neither  books  nor  engravings 
had  given  me  any  conception* 

Some  of  the  individuals  under  our  present  examination 
are  exhibiting  phenomena  of  no  less  interest  than  their 
form  and  motions.  Some  of  the  stalks  are  terminated  by 
two  vases  instead  of  one,  which  appear  to  spring  from  a 
common  point.  These,  however,  are  the  result  of  the 
spontaneous  splitting  of  one ;  and  in  other  examples  you 
may  see  the  process  in  different  stages ;  or,  if  your  patience 
endure  a  couple  of  hours'  watching,  you  may  trace  the 
whole  phenomena,  as  I  have  done,  from  the  moment  when 
it  first  becomes  perceptible,  to  its  completion  in  the  free- 
dom of  one  of  the  newly-formed  animalcules. 

For  instance,  you  perceive  that  one  of  the  bells  instead 
of  being  vase-shaped  has  assumed  a  globular  form.  By 
keeping  your  eye  on  this  for  only  a  few  moments,  you  de- 
tect a  depression  forming  in  the  midst  of  its  front  outline, 
which  momentarily  deepens,  until  it  is  manifestly  a  cleft. 
The  division  proceeds  downwards,  the  two  halves  healing 
simultaneously,  so  that  they  are  at  all  times  perfectly 
smooth  and  rounded ;  at  length  two  vases  appear,  side  by 
side,  where  a  few  minutes  before  there  had  been  but  one. 

One  of  these  is  destined  to  be  ultimately  thrown  off, 
while  the  other  retains  sole  possession  of  the  stalk.  You 
soon  see  which  it  is  that  is  going  to  emigrate  :  for,  though 
the  two  are  alike  in  size,  the  roving  one  early  closes  the 
mouth  of  the  vase,  becoming  smooth  and  globular  there, 
never  to  open  again.  The  cilia,  now  therefore  become 
useless,  disappear  by  absorption ;  but  meanwhile  a  new 


406  EVENINGS   AT    THE    MICROSCOPE. 

circle  of  these  organs  is  developed  around  the  basal  ex- 
tremity of  the  vase,  and  these,  every  instant  becoming 
more  vigorous  in  their  motions,  sway  the  little  globe  about 
on  its  point  of  attachment.  At  length  the  connexion 
yields,  breaks,  and  the  animalcule  shoots  away,  rowed  by 
its  hundred  oars,  to  find  a  new  abode,  and  to  found  a  new 
colony. 

Here  and  there  you  see  shooting  through  the  group, 
with  a  rapid  gliding  movement,  an  oblong  clear  body. 
This  is  one  of  the  vases,  formed  by  self-division,  and  exer- 
cising its  newly  found  power  of  locomotion.  It  is  giddily 
roving  hither  and  thither,  until  the  instinct  of  wandering 
ceases,  when  it  will  soberly  settle  down,  affix  itself  by  the 
point  which  was  formerly  its  mouth,  whence  a  new  stalk 
will  gradually  grow,  and  opening  a  new  mouth  in  the 
midst  of  the  new  crown  of  cilia. 

I  believe  that  the  division  is  sometimes  transverse  in- 
stead of  longitudinal,  the  cleft  occurring  by  constriction 
across  the  middle  of  the  vase ;  but  this  I  have  not  seen. 
In  whatever  direction  it  takes  place,  it  is  essential  that  the 
oblong  granular  body,  called  the  nucleus,  which  you  see  in 
each  vase,  be  divided,  the  cleft  passing  through  the  middle 
of  this  substance,  a  portion  of  which  is  therefore  appro- 
priated to  each  new-made  animal. 

That  the  essential  vitality  of  the  creature  resides  in  this 
nucleus  is  shown  by  another  and  highly  curious  mode  of 
increase,  namely,  that  which  is  effected  by  encyst  ion.  Let 
us  search  the  live-box  carefully;  for,  amidst  so  great  a  pro- 
fusion of  Vorticella  as  we  have  on  this  Nitetta,  it  will  go 
hard  if  we  do  not  find  some  individuals  in  the  encysted 
stage. 

Look  at  this  elegant  object.  It  resembles  a  trumpet  of 
the  clearest  glass,  with  a  rounded  extremity,  and  with  the 
base  affixed  to  the  weed,  from  which  it  stands  up  erect. 
Within  the  expanded  part  of  the  trumpet  there  is  a  turbid 
mass,  with  a  perfectly  defined  outline,  from  several  points 


INFUSORIA. 


407 


of  which  proceed  radiating  pencils  or  tufts  of  long,  straight, 
stiff,  elastic  filaments,  like  threads  of  spun  glass,  varying 
greatly  in  length,  and  each  terminated  by  a  little  knob  of 
the  same  material.  The  tout  ensemble  of  this  object  is 
very  attractive  and  beautiful,  and  its  history  is  a  tale  of 
marvels. 

No  wonder  that  Ehrenberg,  supposing  this  form  to  be 


an  independent  animal,  gave  it  a  generic  and  specific  name. 
He  called  it  Acineta  mystacina.  For  who  would  have  sus- 
pected that  this  stiff  and  motionless  object,  with  its  tufts  of 


408  EVENINGS    AT    THE    MICEOSCOPE. 

flexible  but  inanimate  threads,  had  any  connexion  with  the 
sprightly  vases  which  we  have  been  examining  ?  Yet  it  is 
the  same  animalcule,  in  what  we  may,  with  a  certain 
liberty  of  phrase,  call  its  chrysalis  condition  ! 

The  history  of  the  Vorticella,  as  it  has  been  elaborately 
worked  out  by  Dr.  Stein,  exhibits  phenomena  analogous  to 
those  marvellous  changes  which  we  lately  considered  under 
the  appellation  of  the  Alternation  of  Generations.  Large 
individuals  withdraw  their  circle  of  cilia,  close  up  the 
mouth,  and  become  globular,  and  then  secrete  from  their 
whole  surface  a  gummy  substance,  which  hardens  into  a 
spherical  transparent  shell  called  a  cyst,  inclosing  the 
Vorticella  in  its  cavity.  Within  this  cyst  is  seen  the  hand- 
shaped  nucleus,  unchanged,  and  what  was  the  contractile 
bladder,  which,  however,  no  longer  contracts. 

By- and-by  this  torpid  Vorticella  enlarges  itself  irregularly, 
pushing  out  its  substance  in  tufts  of  threads,  and  frequently 
protruding  from  one  side  a  larger  mass,  which  becomes  an 
adhering  stalk.  Thus  it  has  become  an  Acineta,  such  as 
we  now  behold. 

From  this  condition  two  widely  different  results  may 
proceed.  In  the  one  case,  the  encysted  Vorticella  sepa- 
rates itself  from  the  walls  of  the  Acineta,  contracts  into  an 
oval  body,  furnished  at  one  end  with  a  circle  of  vibratory 
cilia,  by  whose  movements  it  rotates  vigorously  in  its 
prison,  while  the  more  obtuse  end  is  perforated  by  a  mouth 
leading  into  an  internal  cavity.  In  the  interior  of  this 
active  oval  body  there  are  seen  the  band-like  nucleus,  and 
a  cavity  which  has  again  begun  to  contract  and  to  expand 
at  regular  intervals.  It  is,  in  fact,  in  every  respect  like  a 
Vorticella  vase,  which  has  just  freed  itself  from  its  stalk. 
Presently,  the  perpetual  ciliary  action  so  far  thins  away  the 
walls  of  the  Acineta  that  they  burst  at  some  point  or  other, 
and  the  little  Vorticella  breaks  out  of  prison,  and  com- 
mences life  afresh.  The  Acineta9  meanwhile,  soon  heals 
its  wound,  and  after  a  while  develops  a  new  nucleus,  which 


INFUSORIA.  409 

passes  through  the  same  stages  as  I  have  described,  and 
bursts  out,  a  second  Vorticella. 

But  the  cycle  of  changes  may  be  quite  different  from 
this.  For  sometimes  the  nucleus  within  the  Adneta,  in- 
stead of  forming  a  Vorticella,  breaks  itself  up  into  a  great 
number  of  tiny  clear  bodies,  resembling  Monads,  which 
soon  acquire  independent  motion,  and  glide  rapidly  about 
the  cell  formed  by  the  inclosed  Vorticella-'bod.y  as  hi  a  little 
sea.  But,  by-and-by,  this  body,  together  with  the  Adneta 
wall,  suddenly  bursts,  and  the- whole  group  of  Monad-like 
embryos  are  shot  out,  to  the  number  of  thirty  or  upwards. 
The  Adneta  now  collapses  and  disappears,  having  done  its 
office,  while  the  embryos  shoot  hither  and  thither  in  newly 
acquired  freedom.  It  is  assumed,  on  pretty  good  grounds, 
that  these  embryos  soon  become  fixed,  develop  stalks, 
which  are  at  first  not  contractile,  and  gradually  grow  into 
perfect  Vorticella,  small  at  the  beginning,  but  capable  of 
self -division,  and  of  passing  into  the  Adneta  stage,  and 
gradually  attaining  the  full  size  of  the  race. 

Some  forms  of  the  same  family,  Vorticellada,  are  inter- 
esting as  dwelling  in  beautiful  crystalline  houses,  of  various 
shapes,  always  elegant.  All  these  have  been  ascertained 
to  pass  through  the  same  or  similar  Adneta  stages.  Co- 
thurnia  imberbis  is  one  of  the  prettiest  of  these.  The  cell 
is  of  an  elegant  ampulla-like  form,  perfectly  transparent 
and  colourless,  set  on  a  stiff  foot,  or  short  pedicle,  which 
shows  many  transverse  folds,  like  those  of  leather.  From 
the  mouth  of  the  vase  projects  the  animal,  whose  form 
may  be  distinctly  traced  through  the  clear  walls  of  the 
cell  attached  to  its  bottom,  whence  it  stretches  upward 
when  seeking  prey,  or  to  which  it  shrinks  when 
alarmed. 

In  the  former  condition  the  body  resembles  a  much 
elongated  Vorticella,  with  a  similar  circular  orifice,  set 
round  with  cilia.  Often  the  animal  performs  its  ciliary 
vibrations  within  the  shelter  of  its  house,  not  venturing  to 


410  EVENINGS   AT    THE    MICROSCOPE. 

protrude  beyond  its  rim.  If  carmine  has  been  mixed  with 
the  water,  the  atoms  are  seen  in  the  customary  vortex,  and 
some  are  occasionally  drawn  into  the  cell  nearly  half-way 
down  its  cavity,  and  then  swiftly  driven  out  again.  On  a 
slight  tap  upon  the  table  the  animal  withdraws,  and  in  the 
same  moment  the  urn  bends  down  upon  its  leathery 
pedicle,  at  a  point  where  there  is  always  an  angle,  until 
the  rim  of  the  cell  is  in  contact  with  the  plant  to  which 
it  is  attached.  This  action  is  instantaneous.  Presently, 
however,  it  rises,  and  resumes  its  former  position,  and 
then  the  mouth  of  the  cell  slowly  opens,  and  the  animal 
again  protrudes,  the  cilia  appearing  first,  and  finally  the 
head  or  front  part  of  the  animal,  which  is  then  opened  and 
begins  to  rotate. 

Very  similar  to  this  are  the  Vaginicolce,  but  the  cells 
which  they  inhabit  are  not  stalked,  but  are  immovably 
affixed  to  plants.  In  F.  crystallina,  the  cell  is  a  tall  gob- 


VAOINICOLA. 


let,  standing  erect,  perfectly  colourless ;  while  in  F.  de- 
cumbens,  it  is  slipper-shaped,  attached  along  its  sides,  and 
of  a  golden-brown  hue,  but  still  quite  transparent.  Here 
is,  fortunately,  a  group  of  the  latter  species,  scattered 
about  the  leaves  of  the  Nitella. 

Though,  in  general,  both   in  form  and  habits,  closely 
like  the  Cothurnia,  yet  the  Vayinicola  has  some  peculia- 


INFUSORIA.  411 

rities  of  interest.  The  cilia  are  more  developed,  and  can 
be  more  distinctly  seen  than  in  either  Cothurnia  or 
Vorticella,  forming,  when  in  swift  action,  a  filmy  ring 
above  the  margin,  along  which,  as  if  upon  a  wheel,  on*e 
or  more  dark  points  are  frequently  seen  to  run  swiftly 
round :  the  optical  expression,  as  I  presume,  of  a 
momentary  slackening  in  the  speed  of  the  wave.  The 
act  of  self-division  takes  place  in  this  animal,  as  in  the 
Vorticella ;  and  it  is  curious  to  see  two  Vaginicola,  exactly 
alike,  lovingly  inhabiting  the  same  cell.  One  of  the  cells 
which  we  are  now  examining  is  in  this  doubly-tenanted 
condition. 

I  will  now  exhibit  to  you  some  examples  of  the  most 
highly  organised  forms  of  this  class  of  animals,  in  which 
we  discern  a  marked  superiority  over  any  that  we  have  yet 
looked  at,  and  a  distinct  approach  to  those  animals  whose 
more  precise  movements  are  performed  by  means  of  special 
limbs.  These  creatures  are  very  common,  both  in  fresh 
and  sea-water,  wherever  vegetable  matter  is  in  process  of 
decomposition  ;  and  hence  their  presence  can  at  all  times 
be  commanded  by  keeping  infusions.  In  this  old  infusion 
of  sage  leaves,  for  instance,  they  occur  in  vast  multitudes, 
past  all  imagination ;  as  you  may  see  with  a  lens  in  this 
drop. 

This  group  Belongs  to  the  genus  Stylonychia,  and  as  I 
believe,  to  the  species  S.  pustulata.  It  presents  the  form 
of  an  oval  disk,  which,  when  seen  sidewise,  is  found  to  be 
flat  beneath  and  convex  above.  It  commonly  swims  with 
the  belly  upwards,  and,  when  exhibited  on  the  stage  of  the 
microscope,  in  almost  every  case,  this  surface  is  pre- 
sented to  the  eye.  It  darts  about  very  irregularly,  with  a 
bobbing  motion,  rarely  going  far  in  one  direction,  but 
shooting  a  little  distance,  and  then  instantly  receding, 
turning  short  round,  and  starting  hither  and  thither,  so 
fitfully  that  it  is  very  difficult  to  obtain  a  fair  sight  of  its 
structure.  Its  margin,  however,  is  surrounded  by  short 


412  EVENINGS   AT    THE    MICEOSCOPE. 

cilia;  the  mouth,  which  is  a  long  opening  on  the  front 
part,  and  at  the  left  side  (as  to  the  animal)  of  the  ventral 
surface,  is  fringed  with  long  cilia,  which  are  continually 
vibrating.  These  are  the  organs  of  the  darting  motion ; 
but  the  creature  crawls  like  a  mouse,  along  the  stems  of 
conferva,  &c.,  which  it  performs  by  means  of  curved  spines, 
called  uncini,  near  the  front  part,  the  points  of  which  are 
applied  to  the  stem,  and  also  by  long  stiff  styles  or  bristles, 
which  project  backward  and  downward  from  the  hinder 
part.  Sometimes  the  animalcules  crawl  for  a  moment 
back-downward,  on  the  inner  surface  of  the  glass  cover, 
when  the  bases  of  the  anterior  curved  spines  appear 
dilated  like  large  spots.  The  spines  are  not  capable  of 
much  action,  but  they  are  rapidly  used.  The  general 
appearance  of  the  creature  reminds  us  of  the  little  Wood- 
louse  or  Armadillo  of  our  gardens.  The  interior  of  the 
body  is  occupied  with  a  granular  substance,  in  which  are 
scattered  many  globular  vesicles  of  different  sizes.  The 
animal  is  very  transparent,  and  almost  colourless.  They 
increase  very  fast  by  transverse  division,  which  is  per- 
formed under  the  microscope,  so  as  greatly  to  increase  the 
number  under  examination,  even  in  an  hour  or  two.  A 
constriction  forms  in  the  middle  of  one,  which  quickly 
deepens,  dividing  the  oblong  creature  into  two  of  circular 
figure.  The  mouth  of  the  new  one,  with  its  vibratile  cilia, 
is  formed  long  before  separation  is  complete,  and  at  the 
same  end  and  side  as  in  the  parent.  The  styles  and  bris- 
tles then  form,  and  the  creatures  are  held  together  for  a 
few  seconds  by  these  organs,  even  when  the  bodies  are 
distinctly  severed.  When  separated,  they  retain  the 
round  form  for  some  time. 

When  a  drop  of  such  water  is  examined  between  two 
plates  of  glass,  it  is  amusing  to  observe  the  numbers  that 
congregate  in  the  little  pools  left  by  the  gradual  drying  of 
the  fluid.  This  probably  becomes  unfit  for  respiration ; 
for  the  motion  of  the  cilia  becomes  more  and  more  languid, 


INFUSOBIA.  413 

and  the  creatures  die  before  the  water  is  dry.  They  not 
only  die,  but  vanish,  so  that, — where  there  were  scores,  so 
close  that  in  moving  they  indented  each  other's  sides  and 
crawled  over  one  another, — if  we  look  away  for  a  few 
minutes,  and  again  look,  we  see  nothing  but  a  few  loose 
granules.  This  puzzled  me,  till  I  watched  some  dying, 
and  I  found  that  each  one  burst  and,  as  it  were,  dissolved. 
The  cilia  moved  up  to  the  very  last  moment,  especially  the 
strong  ones  in  front,  until,  from  some  point  in  the  outline, 
the  edge  became  invisible,  and  immediately  the  animal 
became  shapeless,  and  from  the  part  which  had  dissolved 
the  interior  parts  seemed  to  escape,  or  rather  the  skin,  so 
to  speak,  seemed  to  dissolve,  leaving  only  the  loose  viscera. 
From  the  midst  of  these  then  pressed,  as  if  by  the  force  of 
an  elastic  fluid  within,  several  vesicles  of  a  pearly  appear- 
ance, varying  in  number  and  size,  and  then  the  whole  be- 
came evanescent. 

You  will  have  observed  that  the  admixture  of  carmine  to 
the  water,  while  the  animalcules  were  active,  shows  the 
direction  of  the  ciliary  motion  with  great  distinctness. 
The  particles  form  two  eddies,  one  on  each  side  of  the 
front,  which  meet  in  the  centre  in  a  strong  current,  and 
pass  off  behind  the  mouth  on  each  side.  We  do  not  per- 
ceive that  any  of  them  swallow  the  particles  of  carmine,  for 
the  internal  vessels  remain  colourless. 

I  have  found  that  if  a  drop  of  water  containing  these 
animals  be  placed  on  a  slip  of  glass  exposed  to  the  open 
air,  they  do  not  burst  as  the  water  dries  away,  but  dry 
flat  on  the  glass,  their  bodies  broader  but  shorter  than 
when  alive,  and  quite  entire.  Their  cilia  are  then  very 
manifest.  On  being  again  wetted,  though  after  only  a  few 
minutes'  desiccation,  I  have  never  been  able  to  revive  them, 
nor  any  other  Infusoria  in  like  circumstances,  notwith- 
standing what  is  stated  in  books. 

Here  is  another  species  in  equally  amazing  profusion, 
8.  mytilus.  Its  form  is  oblong,  with  rounded  extremities, 


414  EVENINGS   AT    THE    MICROSCOPE. 

the  anterior  obliquely  dilated.  This  species  affords  a  good 
example  of  the  various  organs  of  locomotion.  A  trans- 
parent oblong  shield,  which  is  quite  soft  and  flexible,  is 
spread  over  the  back,  which  does  not  prevent  our  eyes 
discerning  all  the  organs  through  it ;  though,  much  more 
commonly,  the  animal,  when  under  the  microscope,  crawls, 
belly-upward,  beneath  the  glass  cover  of  the  live-box. 
Around  the  anterior  part,  which  is  broadened,  are  placed 
cilia,  which  are  vibratile  ;  these  are  continued  round  the 
mouth,  a  sort  of  fold  on  the  side.  Towards  the  posterior 
extremity  on  each  side  are  other  rows  of  cilia,  which  being 
large  are  well  displayed.  On  the  ventral  surface,  chiefly 
towards  the  front  part,  are  seen  several  thick  pointed 
processes,  shaped  like  the  prickles  of  a  rose,  but  flexible, 
and  capable  of  being  turned  every  way.  These  are  the 
uncini,  and  are  evidently  used  as  feet,  the  tips  being 
applied  to  the  glass.  The  optical  effect  of  the  throwing 
about  of  these  uncini,  when  the  place  which  they  touch 
is  in  focus,  is  very  curious.  They  are  rapidly  moved,  but 
without  regularity ;  the  tips  bend  as  they  touch  the 
surface  of  the  glass  ;  some  of  them  seem  to  have  accessary 
hairs,  equally  long,  but  slender,  proceeding  from  the 
same  base.  On  the  hinder  quarter  of  the  ventral  surface 
are  several  thick  pointed  spines  ;  these  are  inflexible,  nearly 
straight,  placed  side  by  side,  but  not  in  regular  order, 
some  reaching  beyond  others.  I  have  not  seen  these  used, 
but  they  commonly  remain  sticking  out  in  a  horizontal 
direction.  These  organs  are  termed  styles.  Besides 
these,  there  are  three  slender  bristles,  called  seta,  placed 
at  the  hinder  extremity,  the  central  one  in  the  line  of  the 
body,  the  others  radiating  at  an  angle.  These  are  dis- 
tinguished from  the  cilia,  not  only  by  their  length,  but  by 
not  being  vibratile.  The  motions  of  these  animals  are 
powerful,  but  irregular  and  fitful,  very  much  like  those  of 
the  former  species.  They  dart  hither  and  thither,  back- 
ward as  well  as  forward,  occasionally  shooting  round  and 


INFUSORIA.  415 

round  in  a  circle,  with  many  gyrations,  much  like  the  pretty 
little  polished  beetles  (Gyrinm)  that  play  in  mazy  dances 
on  the  surface  of  a  pool.  The  two  extremities  seem  covered 
with  minute  pits  or  stipplings,  but  colourless  ;  the  central 
part  is  occupied  with  yellowish  granules  of  different  sizes. 

I  once  witnessed  the  dissolution  of  one  of  these  animals 
under  peculiar  circumstances.  Two  or  three  stems  of  an 
aquatic  plant  had  become  crossed  in  the  live-box  so  as  to 
form  an  area,  into  which  the  Stylonychia  had  somehow 
introduced  himself.  There  was  just  room  for  him  to 
move  backward  and  forward  without  turning,  and  the 
space  was  about  three  times  his  own  length.  Within  this 
narrow  limit  he  impatiently  continued  crawling  to  and  fro, 
moving  his  uncini  with  great  rapidity,  and  showing  their 
extreme  flexibility;  for,  as  he  applied  them  now  to  the 
stem,  now  to  the  surface  of  the  glass,  these  whip-like 
uncini  were  sometimes  bent  double.  The  so-called  styles 
at  the  posterior  extremity,  though  less  frequently  used  so, 
were  yet  occasionally  bent  and  applied  to  the  surface  as 
feet,  so  that  they  are  certainly  not  inflexible  as  supposed, 
nor  do  I  see  any  essential  difference  between  them  and 
the  uncini.  The  whole  body  was  flexible,  taking  the  form 
of  any  passage  or  nook  into  which  it  was  thrust,  yet 
recovering  its  elasticity  immediately  the  pressure  was 
removed.  Its  proper  form  appeared  to  be  convex  above 
and  concave  beneath,  rather  than  flat.  After  having  been 
thus  employed  about  half-an-hour  under  my  observation, 
it  became  still,  moving  only  its  cilia,  when  I  left  it  a  little 
while,  and  on  my  return  found  that  it  was  dissolved  ;  the 
outline  having  entirely  disappeared,  and  nothing  being  left 
but  the  granules,  and  globular  vesicles,  that  had  constituted 
its  viscera,  some  of  which  still  contained  the  carmine 
which  had  been  very  perceptible  in  the  living  animal. 
This  was  the  more  remarkable,  as  there  was  plenty  of 
water.  It  looked  like  suicide, — a  spontaneous  choosing 
of  death  rather  than  hopeless  captivity. 


416  EVENINGS   AT   THE    MICROSCOPE. 

Common  as  these  Stylonychia  are,  and  abundant  beyond 
all  calculation,  where  they  do  occur,  from  their  tendency 
to  self-division,  they  are  not  so  universally  met  with  as 
their  cousins,  of  the  genus  Euplotes.  These  are  still 
more  highly  organised,  and  will  please  you  by  their  ac- 
tivity and  sprightly  intelligence,  I  am  sure.  Here  are 
several  individuals  in  the  live -box  at  this  moment. 

They  differ  from  the  Stylonychice,  in  having  the  soft 
body  covered  with  a  plate  of  crystal  mail,  hard  and  in- 
flexible, much  like  the  shield  of  a  Tortoise.  Several 
species  have  this  glassy  shield  marked  with  delicate  lines 
running  lengthwise  ;  sometimes  in  the  form  of  parallel 
ridges,  as  in  a  little  species  found  in  infusions  (perhaps 
E.  charon),  at  others  forming  rows  of  minute  round  knobs, 
as  E.  truncatus,  the  species  now  before  us.  The  shield  is 
ample,  considerably  overlapping  the  soft  body ;  it  rises 

into  an  arched  form  in 
the  centre  ;  and  is  more 
or  less  round  or  oval. 
The  mouth  is  oblique, 
and  extends  a  long  way 
down  the  under  surface  ; 
it  is  set  with  strong  and 
fine  cilia,  which  also 
spread  over  the  front. 
The  organs  of  motion 

are,  as  before,  long  styles,  pointed  and  rather  stiff  pro- 
cesses, which  project  from  beneath  the  shell  backwards 
and  downwards,  and  soft  hook-like  uncini,  which  are  set 
chiefly  near  the  fore  part  of  the  inferior  surface.  In  the 
species  before  us  these  are  about  six  or  seven  in  number, 
but  in  E.  charon  they  are  more  numerous.  The  twinkling 
rapidity  with  which  these  little  feet  are  applied  to  the 
surface  in  crawling  affords  a  pleasing  sight :  particularly 
when  the  animal  is  running  back- down  wards  on  the  upper 
glass  plate  of  the  live-box.  Some  species  have  bristles 


INFUSORIA.  417 

(or  seta)  affixed  to  the  hinder  part  of  the  shell,  from  which 
they  diverge.  In  E.  truncatiis  these  are  four,  but  they 
are  wanting  in  E.  charon.  The  body  displays  a  mass  of 
granules,  vacuoles,  and  vesicles  of  different  sizes. 

These  are  very  beautiful  objects ;  and  their  sprightly 
motions  and  apparent  intelligence  give  them  an  additional 
interest.  They  crawl  more  than  they  swim,  running  with 
great  swiftness  hither  and  thither,  frequently  taking  short 
starts,  and  suddenly  stopping.  The  specimens  which  we 
are  examining  are  taken  from  water  which  had  been  kept 
in  a  jar  for  several  weeks.  The  vegetable  matters  are 
decaying,  and  among  the  stems  and  filaments  this  pretty 
species  crawls  and  dodges  about.  It  seems  reluctant  to 
leave  the  shelter  of  the  decaying  solution ;  sometimes  one 
will  creep  out  a  little  way  into  the  open  water ;  but  in  an 
instant  it  darts  back,  and  settles  in  among  the  stems  and 
flocculent  matter.  Any  attempt  by  turning  the  glass  cover 
to  bring  it  out  into  view  only  makes  it  dive  deeper  into  the 
mass,  as  if  seeking  concealment.  This  is  about  ^r^h  of 
an  inch  in  length  of  lorica ;  and  the  E.  charon  is  not  more 
than  one-fourth  of  this  size.  These  creatures  remind  one 
of  an  Oniscus,  especially  when  in  profile. 

There  is  an  animal  very  closely  allied  to  these,  but  much 
more  beautiful,  being  of  a  clear  greenish  translucency, 
with  several  vesicles  filled  with  a  rose-coloured  or  purple 
fluid  of  much  brilliancy.  This  creature,  which  bears  the 
name  of  Chlamidodon,  has  the  peculiarity  of  a  set  of  wand- 
like  teeth  arranged  in  a  hollow  cylinder. 

And  with  these  we  dismiss  the  Infusoria,  a  class  of 
animals  which,  from  their  minuteness,  the  number  and 
variety  of  their  species,  their  exceeding  abundance,  the 
readiness  with  which  they  may  be  procured,  and,  as  it 
were,  made  to  our  hand  (by  simply  steeping  vegetable 
matter  in  water),  and  the  uncertainty  which  still  prevails 
as  to  many  parts  of  their  structure  and  economy  ;  and 

£    £ 


418  EVENINGS   AT    THE    MICROSCOPE. 

therefore,  as  to  their  true  affinities  in  the  great  plan  of 
creation, — offer  one  of  the  most  promising  fields  of  research 
which  a  young  microscopist  could  cultivate. 


These  are  Thy  glorious  works,  Parent  of  good, 

Almighty ;  Thine  this  universal  frame, 

Thus  wondrous  fair.    Thyself  how  wondrous  then  1 

Unspeakable,  Who  sitt'st  above  these  heav'ns, 

To  us  invisible,  or  dimly  seen 

In  these  Thy  lowest  works ;  yet  these  declare 

Thy  goodness  beyond  thought,  and  power  divine. 


THE  END. 


INDEX. 


Acineta,  407. 

Acontia,  356. 

Air-tubes  of  Fly,  95. 

Alcyonium,  349. 

Alternation  of  Generations,  324. 

333. 

Amoeba,  378. 
Anchors  of  Synapta,  299. 
Animalcules,  389. 
Antennae  of  Chafer,  162. 

Crab,  171. 

Fly,  166. 

Gnat,  166. 

Insects,  158. 

Moths,  163. 

Skipjack,  163. 

Weevil,  160. 
Aphrodite.  263. 
Arcella,  383. 

Barnacles,  192. 

hand  of,  192. 

Transformations  of,  195. 
Bee,  eyes  of,  170. 

foot  of,  119. 

mouth  of,  142. 

sting  of,  125. 

wing  of,  73. 
Beetle,  mouth  of,  138. 
"  Bird's-head,"  64. 

use  of,  68. 
Blood  of  Beasts,  27. 

Birds,  28. 

Fishes,  28. 

Frog,  29. 

Man,  27. 

Reptiles,  28. 

Tunicate,  33. 
Brachionus,  225. 
Bristle-tail,  scales  of,  77. 


Bug,  mouth  of,  143. 
Bugula,  64. 

Butterfly,  scales  of,  79,  80. 
sucker  of,  153. 

Caryophyllia,  weapons  of,  364. 
Chameleon-fly,  101. 
Cheese-mite,  220. 
Chilomonas,  401. 
Chirodota,  298. 
Cicada,  drum  of,  89. 

ovipositor  of,  136. 
Cilia  of  Cydippe,  310. 

Infusoria,  397,  403,  409. 

Rotifera,  223,  252. 
Cinclides,  358. 
Cnidae,  342,  356. 
Cockchafer,  antennae  of,  162. 

spiracle  of,  100. 
Coleps,  399. 
Contractile   Bladder,    250,    380, 

397. 

Corkscrew  Coralline,  63. 
Corynactis,  weapons  of,  369. 
Cothurnia,  409. 
Cows'  paps,  349. 
Crabs,  171. 

ears  of,  172. 

eyes  of,  174. 

stages  of,  182. 
Crane-fly,  spiracle  of,  99. 
Craspeda,  364. 
Cricket,  drum  of,  85. 
Cuckoo-fly,  ovipositor  of,  128. 
Cuttle-shell,  39. 
Cyclops,  175. 
Cydippe,  308. 
Cypris,  180. 

Daphnia,  178. 


420 


INDEX. 


Dead-men's  fingers,  349. 
Diamond-beetle,  scales  of,  83. 
Dragon-fly,  71. 
eye  of,  166. 

Dumb-bells  of  Holothuria,  297. 
Dyticus,  foot  of,  117. 

Earthworm,  259. 
Ecthoraeum,  366. 
Egger-moth,  163. 
Euglena,  389. 
Eunice,  268. 
Euplotes,  416. 
Eyes  of  Crab,  174. 

Dragon-fly,  166. 

Harvestman,  209. 

Infusoria,  389. 

Insects,  166. 

Rotifera,  236,  389, 

Scallop,  50. 

Snail,  54. 

Spider,  207. 

Feathers,  structure  of,  15. 
Fission  of  Infusoria,  394,  405. 
Flea,  mouth  of,  146. 
Fly,  antenna  of,  166. 

flight  of,  70. 

foot  of,  115. 

spiracle  of,  98. 

tongue  of,  151. 

wing  of,  72. 
Foot  of  Actinurus,  249. 

Bee,  119. 

Beetle,  117. 

Brachion,  227. 

Dinocharis,  241. 

Fly,  109. 

Silkworm,  123. 

Spider,  217. 

Whiptail,  239. 
Foraminifera,  383. 
Frog,  blood  of,  31. 
Froghopper,  ovipositor  of,  135. 

G-alathea,  186. 

Gall-fly,  egg-tube  of,  128. 

Gnat,  antennae  of,  166. 

grub  of,  103. 

mouth  of,  149. 

wing  of,  74. 
Grantia,  386,  388. 
Grasshopper,  sounds  of,  86. 

Hair  of  Bat,  12. 
Bee,  14. 
Beetle,  14. 


Hair  of  Cat,  8. 

Hog,  5. 

Horse,  7. 

Man,  2. 

Mole,  9 

Moth,  14. 

Mouse,  11. 

Sable,  9. 

Sheep,  7. 

Halichondria,  386. 
Harvestman,  209. 
Heart-urchin,  292. 
Horse-fly,  mouth  of,  145. 
House-fly,  70. 
Humble  bee,  71. 
Hydractinia,  334. 

Infusoria,  389. 
Insects,  70. 

air-tubes  of,  93. 

antennae  of,  158. 

eyes  of,  166. 

feet  of,  109. 

mouths  of,  138. 

sounds  of,  84. 

stings,  &c.,  of,  125. 

Jelly-fish,  307. 
Katedid,  86. 

Laomedea,  326. 

meduso'ids  of,  331 . 
Lares,  345. 

Larva  of  Urchin,  301. 
Leech,  269. 
Limpet,  tongue  of,  46. 
Locomotion,  variety  in,  258. 
Lombrinereis,  268. 
Luminosity  of  Medusa,  319. 
Lynceus,  177. 

Madrepore,  weapons  of,  364. 
Mastax,  233. 
Medusae,  307. 

transformations  of,  333. 
Meduso'ids,  of  Laomedea,  331. 

Stauridia,  343. 

Mite,  cheese,  220. 

water,  222. 
Mollusca,  ears  of,  55. 

eyes  of,  51. 

shells  of,  39. 

tentacles  of,  50. 

tongues  of,  46. 
Moths,  antennae  of,  163. 


INDEX. 


421 


Moths,  scales  of,  79,  81. 
Mouth  of  Bee,  142. 

Beetle,  138. 

Brachion,  230. 

Bug,  143. 

Flea,  146. 

Gnat,  148. 

House-fly,  151. 

Sea- worm,  267. 

Swordbearer,  246. 

Tube-wheel,  251. 

Whiptail,  238. 
Murder,  discovery  of,  25. 

Nacre,  43. 

Nais,  262. 

Nucleus  of  Infusoria,  406. 

Nymphon,  218. 

Otolithes  of  Medusae,  320. 

Slug,  56. 
Ovipositor  of  Cuckoo-fly,  128. 

Gall-fly,  128. 

Saw-fly,  131. 

Paramoacium,  396. 
Pearls,  44. 
Pedicellariae,  282. 

structure  of,  282. 

use  of,  288. 
Periwinkle,  eating  of,  49. 

tongue  of,  50. 
Perophora, 

circulation  in,  34. 

respiration  in,  36. 
Phyllodoce,  265. 
Pleasures  of  Sea-shore,  325. 
Podura,  scales  of,  78. 
Polymorphina,  383. 
Polynoe,  262. 
Polypes  of  Alcyonium,  350. 

Hydractinia,  334. 

Laomedea,  326. 

Lar,  348. 

Polystomella,  383. 
Polyzoa,  60. 
Proteus,  378. 
Protozoa,  376. 
Pseudopodia,  384. 

Robber,  story  of,  2. 
Eotifera,  223. 

Sabella,  343. 
Sagartia,  356,  3G6. 


Sarsia,  313. 

Saw-fly,  ovipositor  of,  130. 
Scales  of  Butterflies,  79. 
Bristle-tail,  77. 
Diamond-beetle,  83. 
Flounder,  21. 
Gnat,  75. 
Gold-fish,  19,  24. 
Perch,  17. 
Pike,  23. 
Podura,  78. 
Sugar-louse,  77. 
Wrasse,  21. 
Scallop,  eyes  of,  50. 
Sea-anemones,  weapons  of,  315. 
Sea-cucumber,  296. 

dumb-bells  of,  297. 
Sea-mat,  59. 

Sea-mouse,  bristles  of,  264. 
Sea-shore,  pleasures  of,  325. 
Sea-urchin,  spines  of,  277. 
larvae,  301. 
pedicellarise,  282. 
pores,  290. 
skeleton,  302. 
suckers,  305. 
Serpula,  271. 
Shell  of  Cuttle,  39. 
Pearl-oyster,  42. 
Pinna,  42. 
Shore-crab,  182. 
Silkworm,  foot  of,  123. 

spinner  of,  157. 
Skeleton  Wheel-bearer,  241. 
Slug,  ears  of,  55. 

tongue  of,  46. 
Snail,  eye  of,  54. 
Spicula  of  Alcyonium,  352. 
Chirodota,  299. 
Fish-scales,  24. 
Holothuria,  298. 
Sponges,  385. 
Synapta,  299. 
Spiders,  eyes  of,  207. 
fangs  of,  205. 
foot  of,  217. 
habits  of,  210. 
silk  of,  211. 
spinner  of,  213. 
Spines  of  Heart-urchin,  292. 

Sea-urchin,  277. 
Spinner  of  Silkworm,  157. 

Spider,  213. 

Spiracles  of  Insects,  97,  106. 
Sponges,  spicula  of,  386. 

Sting  of  Bee,  125. 


422 


INDEX. 


Stylonychia,  411. 

Suckers  of  Sea-cucumber,  296. 

Sea-urchin,  288. 
Sugar-louse,  77. 
Swan-neck,  393. 
Sword-bearer,  246. 
Synapta,  299. 

Tentacle  of  Cydippe,  309. 

Hydractinia,  339. 

Laomedea,  329. 

Scallop,  50. 

Thaumantias,  319. 
Thaumantias,  319. 
Tongue  of  Butterfly,  154. 

Fly,  151. 

Limpet,  46. 

Periwinkle,  46. 

Slug,  46. 

Trochus,  47. 
Trachelocerca,  393. 
Transformations  of 

Barnacle,  195. 

Grab,  182. 

Galathea,  188. 

Medusa,  323. 

Polype,  324. 

Sea-urchin,  301. 

Tube-wheel,  256. 

Vorticella,  408. 


Tripod  Wheel-bearer,  248. 
Trochus,  tongue  of,  47. 
Tube- wheel,  251. 
Turns,  321. 

Urchin,  Sea,  276. 

Vacuoles,  381. 
Vaginicola,  410. 
Vorticella,  402. 

Water-fleas,  175. 

Weapons  of  Anemones,  355. 

Corynactis,  369. 

Madrepore,  364. 

Sea-worms,  262. 
Weevil,  160. 

Scales  of,  83. 
Wheel-bearers,  223. 
Wheels  of  Brachionus,  226. 

Chirodota,  298. 
Whiptail,  238. 
Wing  of  Bee,  73. 

Fly,  72,  84. 

Gnat,  74. 
Wool,  13. 
Worms,  258. 

Zoea  of  Crab,  181. 
Zoophytes,  325. 


LONDON: 

PRISTBD  BT  its.  TRUSCOTT  A 
Suffolk  Lane,  City. 


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HIDDEN  WORKINGS.      By  Miss  H.  R.  RUSSELL,  author 

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HIDE   AND    SEEK  :   A  STORY  OF  THE  NEW  FOREST  IN 

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How    WILLIE    BECAME    A    HERO.      By  the  author  of 

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INVASION  OF  IVYLANDS  (THE).     By  ANNETTE  LYSTER, 

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JOHN    HOLBROOK'S    LESSONS.     By   M.   E.   PALGRAVE, 

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KING'S  HARDEN.     By  the  author  of  "  Our  Valley,"  &c. 

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KITTY  BLIGH'S  BIRTHDAY.     By  ALFRED  H.  ENGELBACH, 

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LAPSED,  NOT   LOST;    A  STORY  OF  ROMAN  CARTHAGE. 

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MARCEL'S  DUTY  :   A  STORY  OF  WAR-TIME.     By  MARY 

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MATE  OF  THE  "LILY"  (THE);  OR,  NOTES  FROM  HARRY 
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MIKE;  A  TALE  OF  THE  GREAT  IRISH  FAMINE.  By  the  REV. 

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MIMI  :    A  STORY  OF  PEASANT  LIFE  IN  NORMANDY.     By 

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MISCELLANIES    OF    ANIMAL     LIFE.       By    ELIZABETH 

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MISSY   AND   MASTER.      By   M.    BRAMSTON,  author   of 

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4  PUBLICATIONS   OF  THE   SOCICTV. 

s.  d. 
MY  LONELY   LASSIE.     By  ANNETTE  LYSTER,  author  of 

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ROUND    MY   TABLE.        By   H.  L.  CHILDE-PEMBERTON, 

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SLAVERS  AND  CRUISERS.     By  S.  W.  SADLER,  Esq.,  R.N., 

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STEFFAN'S    ANGEL,  AND    OTHER    STORIES.      By  M.   E. 

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SV/KET  WILLIAM.      By  Mrs.  THOMAS   ERSKINE.      With 

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THROUGH  THE  ROUGH  WIND  ;  A  STORY  OF  THE  COLLIERIES. 

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UNDER   THE   TREES.     By  H.  L.   CHILDE-PEMBERTON, 

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UNTO   HIS    LIFE'S  END.     A  book  for  choir-boys.     By 

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WHITE  CHAPEL  (THE);  A  STORY.      By  ESME  STUART, 

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